I can counter-recommend Kenney's game assets, it's got sprites, buildings, terrain, backgrounds, top-down, side-on, isometric... Lots of variety for different genres and settings, too.
I always wondered why art is never licensed like software. There is a plethora of free software but I thought very little similarly licensed art. In fact, I think it's just that I wasn't looking. There's lots of it around.
https://lpc.opengameart.org/
There's also a character generator with plenty of options to choose from:
https://liberatedpixelcup.github.io/Universal-LPC-Spriteshee...