The proportions on your characters are pretty bad, that is a big area I would recommend focusing on going forward. Also your models are very unoptimized, there are a lot of edge loops that are unnecessary, especially in your props. I would also recommend rendering them in a game engine like Marmoset instead of the flat…
I disagree on using more polies - if you are really bent on working for DS/iPhone games you're off fine with lowpoly stuff. In fact I'd say work lower poly - especially on the characters. If you're aiming for low spec stuff, this thread and the lowpoly thread are interesting for you. But mostly - you'll need to improve the…