Wow, that edit really brought attention to my lack of darks. :0 Here's an update, trying to keep that point in mind:



A few things I notice now that I look at it again:
-My eyes are immediately drawn to the right (our left) shoulder. I think maybe there's too much contrast there? Or not enough elsewhere?
-Somehow, parts of the shirt (mostly on the left (our right) shoulder) look flatter, even though I added darks to try and give it depth.

Also messed around with the palette some more, hue shifts are fun!

Oh, and one more thing. I'm probably making this way too detailed now for my project, any advice on how I can simplify it without making it cartoony? I feel like I'll need to get rid of a lot of the wrinkles for that, but I dunno which ones are important enough to keep. xP

Seems to me that there's a lot more colors than there needs to be. I'm sure you could considerably reduce your palette by reusing some of those blues in the gray areas, or vice versa.

Alright, tried to listen to some of Helm's advice, and also managed to take it down to 12(?) colors. Color counter says I have more, so I must have overlooked some colors that I tried to get rid of.



I'm aware of techniques like dithering and all that good stuff, but there's a reason I'm trying to avoid using them, at least for this piece. See, when I'm satisfied with it, I'll be constructing it in 3D with a layer of cardboard for each color. If that's not a good enough explanation, here's a sample of what it'll look like, kinda:


So each color a different layer, with it getting higher as the color gets lighter. Maybe it won't be that awesome, but I have confidence that it at least won't look horrible. :3

Obviously if I were to use dithering, the end result would be a nightmare to create, as there would definitely be a lot of single pixels to cut out. So I'll stick to cel shading, at least for this one.

I think posting your reference would help others to critique. Pardon if this is a bit presumptuous on my part, but I believe this is the pose you're trying to replicate:



With the regular Tyrannomon color scheme, of course.

I don't think you should call it done yet, there's still a lot you can do with this! First of all, there's some proportions that need a little tweaking. Here's my edit next to yours(sorry for white background, using Paint right now):


Now, mine is definitely not perfect, and I didn't fix everything. Just wanted to get you a little more on track.

There's a lot more detail work you can do, too, like all those muscles. That'll be fun. It'd look pretty sweet if you textured his skin to look more scaly, but I'm not the one to go to for things like that. xD Anyway, good luck!