A contributor to my art team disagreed that the wood floor tiles needed a fewer number of colors. He did his own modification to my images and explained what he did. In the interest of sharing knowledge, I have re-posted what he did below.


Step number 1:

For a tile that is to represent a flat surface, the luminosity values therein should be normalized to within a small range of values. I've also reduced the spacing between the boards because the boards should be flush with one another, and as far as our pixels go, that makes the spacing between them infinitesimally small compared the individual pixels.  The only reason we draw a line for that is because it's an important detail to show, and there would actually be other ways of making that edge apparent, although this is the one that we're going to use for now.


(these images show the two unique tiles you posted, on the opposite diagonals).


Step number 2:

Desaturate, and drop the luminosity of the whole tile.  This is similar to what is actually done, most of the time, in RPGs like chrono trigger.  You might think that the tile is really bland here and now but you need to keep a wholistic perspective on the design of the game.


Notice how a sprite placed on this leaps out.
Now, we could call it quits here, but there's more fun to come...


Step number 3:

Add a VERY SUBTLE highlight to the top ends of the boards.  Even I initially overdid this, and the image you see is half of what my first guess at an appropriate value turned out to be.



And that wraps it up.  Here are the two tiles you've got now:





Looks pretty awesome to me. I wish I could say I did it all by myself, but then again I am a neophyte to this.

I'm more of a programmer than an artist, but I like to dab into the artistic side every once and a while. The following art I created for my game, Hero of Allacrost. Let me know what you think and how I can improve it.

Wood Floor
Tiles:


Set: (I didn't make the sprite, but that's the protagonist for the game there)


Wood Post

Tiles: (I made two kinds of bases here to see how they would look. I think the second one is better)


Set: (I didn't make the sand)


Shovel




Obviously the shovel needs a lot of work. It's supposed to be made so that it's standing up and leaning against the wall, but I couldn't quite figure out how the shadow should go for that to look right. 


On a related note, are there any good tutorials/tips you can give me for doing pixel art in different perspectives? For some reason I can't seem to do anything well at all unless it's face-on.