I love the style of your sprites; they're very cute. Overall, they look very good. You're right that the old man doesn't look like he's hunched over, though, and I think it's mainly the way he's animated. He looks like he's stomping around, which doesn't really suit someone with terrible old-man posture, hahah. Make his steps slower, and more hobble-y? Some old people even shuffle instead of walking...left foot far forward, then have the right just slide enough to catch up, then put the left foot forward again, never crossing the two legs. That'll probably make him look much older. Right now it looks like he has his dukes up, ready to box someone into submission. Which is pretty awesome in its own way, but... =)
His pants look baggy enough though, and the color is fine. And the style of your sprites really is great, I think!