Fadatar:
What's up with the sides of his face? Looks like somebody took a few nibbles out of it...
I think the eyes could be a bit more colorfull, but that's just me =P
It also lacks some propper AA, and is a bit... flat.
Random Face:
The AA isn't that great, you should refer to some tutorials.
Use two different grays to AA it, not just one light gray.
Random Guy:
Reminds me of a Mii. Interesting style, but where's the arms?
The background is something i've never seen before. I like it.