You've made some really great progress! That sword looks dope. I'd suggest changing the right leg wrinkles into larger shade layers, or just having half of that leg have a shade layer, similar to the hair. A while ago, I helped a friend of mine who's studying game design with some game art. The goal was to create a small working fighting game with friends as main characters. Made a nice background and a sprite, but yours is already cooler though. But your artstyle reminded me of my own style. I use Adobe Illustrator instead of Inkscape. 
Yeah, it's a total bitch to get right, because if you want to change something small you gotta change it on every single symbol. Here's how just the walking animation looked like, which was something like four hours of work: And these are just twelve. Took sixteen for one punch. But it was just a side project, so no big deal. I feel bad for the Skullgirls art designer, that must have been a ton of work.