The Cartographers Guild has a bunch of beautiful images for map inspiration
Having a cohesive visual style is important! This shows what to include and how.
Simon Kopp (Ori and the Blind Forest) talks about art and video games.
Control500 on art for games
If you are a newcomer artists or a student trying to get into concept art, you should read this article. It might clear up some things.
ArtStation - GRABOVER (WIP GAME) Suricate Games, Serge Samsonov
Cartoonic Game Assets