I'm work on a character art and want some advice on proportions and how to add detail.
Any other advice would be appreciated.
https://pbs.twimg.com/media/GjM4ljTWgAAuVKQ?format=png&name=large
My best suggestion for proportions is to look for a human proportions guide via whatever search engine you prefer. You should be able to easily find something useful. Adding details is more complicated, though. That depends on what program you're using, how much detail you want, if you're using a limited palette, etc.
My overall advice is to use reference. When doing game art, I always create a collage of reference images for whatever style I'm trying to go toward and just some general images that are useful.
Anatomically, I would say the things that seems off to me are:
a) Arms too long, e.g. elbow should be higher than navel.
b) lack of waist/hip curve, especially in front view.
Bar from those, the character is recognisable, seems quite usable in a game, I like it!
If you go for such a simple low color pixel art, I would suggest you make a much smaller character!