The main art areas in game development is Concept, Modeling, Texturing and Animating.
Makes the design visible for others so it can be talked about and made into something real. Most concept artists have a unhealthy relation to the company Wacom.
Create meshes for characters and objects using 3d software such as Max or Maya. Make sure you know what side of Maya/Max the artist is on before approaching. If you are not sure default to saying something mildly negative about Blender.
Create textures to be used on meshes, as GUI elements or as backdrops. Prone to fold up in a corner and cry if you install Gimp on their computer.
Animate meshes to create characters that move and act. All animators have strange props like guns or swords that they play around with when thinking about the next animation.
Images where the focus is one the pixel level.
Art Shops & Producers
Reference
Kenney game assets - 2019
Art Design Deep Dive: Using a 3D pipeline for 2D animation in Dead Cells - 2018
real-time-rendering: an overview for artists - 2017
Graphic Research Meshes - 2017
GPU Performance for Game Artists - 2017
Tech Art in Tamriel: The Elder Scrolls Online's Character Tools and Pipeline - 2017
Making a Standard (and Trying to Stick to it!): Blizzard Design Philosophies - 2017
City builder games: make Build-Up animations cheaply - 2015
Don’t go to art school - 2013
Attracting and keeping artists on an OSS game project - 2012