Right now I'm seeing lots of problems here. Before you begin the walk cycles it might be a good idea to re-arrange priorities and work on the original sprites. Some reasons:
Lots of errors in anatomy and structure on both of them. Looks like you tried to put arm muscles on the first guy, but they didn't come out too well.
On top of that (no pun intended), the character designs could use some work. Mutant man doesn't look very "mutated", at least not what I'd expect. It could be a cheap halloween costume, actually. Same with the other. No offense, in either case.
Style seems undefined as well. What are you going for? Cartoony? Or something more serious?
Aside from that, the tileset's lineart is messy and can still be clearly seen, and the ground tiles look a bit like water/sludge. Recently I've been hearing fellow pixellers recommending a more painterly approach, building up from darker colors.
Some examples of rock tiles for you to look at might help. I'll dig some up and edit the post, although they're easy to find, really. (Mainly old RPG games, and some tiles by well-known pixel artists.)
May redo a sprite as an example.