[mhitza]

When I was playing around with Godot and 2D game development, I went to itch.io for free asset packs. It's hard to get a consistent art-style, but good enough for a beginner.

[opyate]

If you have 10 bucks lying around, the comprehensive Kenney pack is good value (on sale, usu. $20), and with consistent art styles.

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

(no affiliation, it's just good stuff)