Nice work on the colours, I really have a problem with the way you shade, your shading style is very subtle but also very well done, still, it makes your characters look like cilinders, if you imagine them in a 3d space. Maybe it's just a style, but I'd really like to see you try a bit more complex anatomy, just to be sure you're on the right track. It's just an opinion though, take it as you will.
I don't want to be the 5 star guy here, but again, there's no big mistake here. Still, the shoulders on the first guy are just wrong, and the 4th guy (from left to right) has his left shoulder out of place. Theese tiny mistakes could kill your pics in the long run.