Can I use the art I find here? How should I credit the artist?
Yes, you can use any of the art submitted to this site. Even in commercial projects. Just be sure to adhere to the license terms. Artists often indicate how they would like to be credited in the "Copyright/Attribution Notice:" section of the submission. You can find this between the submission's description and the list of downloadable files. If no Copyright/Attribution Notice instructions are given, a good way to credit an author for any asset is to put the following text in your game's credits file and on your game's credits screen:
"[asset name]" by [author name] licensed [license(s)]: [asset url]
For example:
"Whispers of Avalon: Grassland Tileset" by Leonard Pabin licensed CC-BY 3.0, GPL 2.0, or GPL 3.0: https://opengameart.org/node/3009
OpenGameArt Search + Reverse Image Search
Hint: Start search term with http(s):// for reverse image search.