Here's some nice useful things to check out (if you havent already) that i like to look at to improve or just watch for inspiration
FYI i learn more from watching things so most of these are gonna be video tutorials, artists talking while painting and timelapse paintings, since i prefer analyzing peoples workflow and try it out than straight tutorials that tell you what to do (not there's anything wrong with it though :P)
LEVEL UP: https://www.youtube.com/user/levelupsessions
omg.... the amount of stuff you can learn from these amazing artists is crazy! i suggest watching from session 1 till the latest. you cant miss a thing these guys say