For those of you who, like me, have no graphical chops whatsoever, I can't recommend Liberated Pixel Cup assets enough:

https://lpc.opengameart.org/

There's also a character generator with plenty of options to choose from:

https://liberatedpixelcup.github.io/Universal-LPC-Spriteshee...

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.

https://kenney.itch.io/kenney-game-assets