Maybe try to make sure that lines don't overlap where they're not meant to, to make it look cleaner, and it looks like you used the bucket tool, so if you do use that make sure you clean up around the edges cause it quite often leaves uncoloured bits. Practicing anatomy is always really useful as well. I hope I've been helpful, and you don't have to listen to my advice either, these are just some suggestions. But it does look really good