Oh good! It didn't seem like it to me because your trees looked so drastically different, sorry about that.  

Hah, I used that same reference picture to churn up an example, but reconsidered posting it since it wouldn't have really helped with the stuff I wrote. Good old google!
Alright, so right now I'll come out and tell you not to worry about style yet. Just try to reconstruct what you see for now. Lemme suggest something that you may or may not be used to doing; draw a tree's silhouette using only negative space. I'd say that you will want to try an oak tree or something that has a more dense leaf structure than a palm tree. Just try to pick out the shapes the sky makes around the tree and through its leaves. In fact, for all of the trees you draw, don't try to draw a tree; draw only the shapes and lines you see that make up the tree.

I'm liking your new tree. Although I still feel like the leaves don't have quite enough contrast. By contrast I do not mean the value of the shades you've chosen; they're plenty contrasting enough in that respect. Look at that palm tree reference you posted, and notice how the shades are distributed.
This is what I see:

The leaves are actually much more isolated in terms of value because some of the leaves are in shadow with only the ambient light from the sky to keep them colorful, while others are getting hit full on by the sun. Leaves will never ever all have the same about of sunlight hitting them, not even close to that actually. Try to distribute your shades accordingly, and refrain from using all of your shades for each leaf or leaf cluster. This is always best to work out in the very early stages of your art since the more work you put into something the more attached you get to it, and it's really hard to get it all right your first try. I did a lot of reworking just for that little example.

Another thing to remember is that you don't wanna make a straight color ramp of green and a straight ramp of brown for the leaves and trunk respectively. In your reference picture there's a lot of blue and yellow in its leaves, and it will make your art pop out and tell everyone, "I'm a tree!" if you can find the actual colors that make it up. Generally, things slowly hint towards yellow as they get lighter and tint towards blue as they get darker because of the sun and sky. Or, if you're doing a piece with different lighting, then just remember that warmer = lighter colors and darker = cooler colors. Just remember that for a guideline though. Just play around with hue shifting as we call it and find something that you like to use.
Here are the colors I see in the trunk and leaves:

Also notice how I began working in the details. What I did was try to emulate the actual leaf structure by first making those light lines through the middles where I saw them on the reference picture. Then I drew a couple more lines out from the middle lines and within the silhouettes I created earlier, and finally drew some of the leaves sticking out of the big blob of color, and made little indentations where the leaves weren't. It was super easy to get the leaves worked in that way than just muscling through it all all at once. That's the reason I said to observe meticulously, and really study how a tree or anything works. Just remember that details aren't very welcome in a piece until you've got the basic idea down really nicely because theres always major structure issues that need to be fixed after the first couple tries, and it's really easy to fix them without any details.

So yeah, don't draw a tree, don't draw tree colors, observe the shapes, and let the image itself tell us it's a tree.  

Firstly my apologies for drawing the wrong gender, but I like drawing girls so that was half the reason I made this edit



Firstly, it looks like his right (our left) eye is about to fall off the side of his face. It's good to make sure you've got some skin showing at the very edge of the head since peoples' eyes are more in the middle of the head, and it only makes sense. Secondly, the bridge of his nose seems to be too flat; I understand this is anime, but even though it breaks most anatomy rules, you need to know how to break them to make it look good. Thirdly, his hair looks too much like rolls of paper, and not quite hair-like. It's good to make each section bleed into the other just slightly to keep it unified and hair-like. Your hair also seems a little lopsided. Fourthly, he doesn't have much of a chin, and no lips. Lips can be hard to pull off, since you need to be really subtle, but it's possible, and looks great if you can get it. Fifthly, the heck it's a neck! It connects to the back of the head, not the bottom. The very front of it is actually right under the very back of the jaw. Sixthly, the eye sockets would leave a noticeable cavity in the right (our left) side of his face. Seventhly*, the proportions are pretty anime right now, and I think that you should try drawing more realistic faces.

That was the anatomy I hope that I fixed up. I'd suggest you do some life studies and maybe pick up an anatomy book to read if you wanna get really great at drawing faces.
* I tried to keep your proportions since I didn't want to deviate too much from the vibe of your character.
 
Note:To make this look male, just try to get some more sharp angles, a more defined neck, and a more pronounced jaw.

Now I think I'll talk some pixel-tech at you. 

So firstly, there's a lot of banding going on everywhere. It's most noticeable on his jawline, but it's hiding in little nooks and crannies everywhere. Try to stay away from long lines of a single shade; if you do that, chances are you'll dodge a lot of blurriness. Secondly, you're spreading your shades out too evenly. I know it feels like a sin to abstain from using all of the colors you have everywhere, but if you bite your lip and choke your cat, you'll be able to overcome that and be able to reserve some of your colors for the more attention-hungry and important parts of your piece, and make it look amazing*. Thirdly, this goes pretty well next to secondly, your pixel clusters (the globs of pixels like the highlight on his cheek left (our right) cheek) are a little too small in some places. Don't be afraid to make some sharp edges and let the pixels shine through in all of their glory. You'll be surprised at how good they can look sometimes, and how much more alive your art will be without all of that super smoothness.

*Please note that my edit does not exploit what I've been talking about enough to be even close to amazing, and I definitely don't think it does. I just like to be emphatic

Well, first I'd just like to say that you miiiiiiiiight wanna get rid of that seam over his crotch.

A good rule to keep in mind for a guy is to downplay his legs and hips as mush as possible. I'd move the orange things to wrap around him somehow to keep it from making him look stocky. It might be good to define the muscle sections a bit more; don't make his arms any bigger, just put in some sharper lines. Lastly consider making the shoulder pads a bit bigger, give him some more of a neck, and build up his traps.

Maybe a sider stance could help too. Here's a nasty edit since I'm not the best at explaining things:


I really like the helmet! that thing looks so awesome.

Hello! I also made you an edit.


Some things to remember are that when working at this size, you're implying much much more than defining. The prime example I see in your sprite is the buttons on his shirt. They are unnecessary, and clutter up your image so that the more important things get lost in the details. Just try to imply hands, don't actually draw them.

You seem to be pillow shading—or not defining a light source and making things lighter as they move towards the middle of the section—instead of actually shading. There are really three different "stages" of shading evolution in an artist. The first is what I just talked about, the second is contour shading, where you shade each section by its shape in two dimensions—sometimes disregarding how each part reacts to the other. And then finally form shading where you shade a lot like a sculptor, cutting and curving, trying to dig into the canvas and really bring out the third dimension. Really strive to get to this form shading.

Your character's anatomy seems a little bit disjointed. I'm not sure what say for this other than, look at naked people! Or as little clothing as you can stand. Then look at people with clothes on to see how the fabric works. Please note that my edit is not even close to perfect in this regard.

EDIT: I'd also suggest to lower the value of your skin tones a bit. I didn't play with the colors of your sprite that much, so just keep that in mind.