These look good! I especially like the falco one, it's the strongest in my opion.
I think you could work on showing depth by restricting the amount of colors you use on a section. What I mean by that is that both of fox's boots have the same colors, and go to the same extreme highlights and shadows. This makes it difficult to tell which leg is infront and which leg is behind at a first glance. You almost have this fixed on the leg, with the most bright yellow not showing up on the back leg, but I think it could be emphasized even more.
I don't know how much sense that made, but I hoped it helped. Good luck pixeling!
It bugs me how Falco's muzzle flair is in his silhouette, but Fox's muzzle flair is absent.
si j'étais encore un gamin j'me serais branler sur ça : )