Kenney Game Assets
Kenney publishes cohesive packs spanning 2D, 3D, interface, audio, and placeholder content that can be downloaded and used immediately.
Why use it
It lets indies prototype quickly without licensing friction while leaving room to replace placeholders with original art later.
Where it fits
Use art, animation, audio, levels, and narrative to make the game easy to read and its world convincing.
What to check
Check the notes bundled with each pack, and remember that the library's popularity can make unmodified assets visually familiar.