Supercell games art style
There's a lot of graphics design inspiration to be had from their games from Clash of Clans, Brawl Stars, Clash Quest, and even Hay Day.
Most of them are pretty simple to look at but very stylistic. This could be seen directly from their media page.
A lot of them is a good starting point for art (e.g., illustration, 3D modelling).
This is especially true for their recent games especially the spin-offs from established universes (e.g., Clash Quest, Clash Mini). They designed it to look different but completely familiar with their gameplay and associated tropes. It really is one of my role models for game design except for the mobile-oriented inconveniences, of course ;D.