Zabin, Daneeklu, Jetrel, Hyptosis, Redshrike, Bertram
http://opengameart.org/content/rpg-tiles-cobble-stone-paths-town-objects

Lanea Zimmerman (AKA Sharm)
http://opengameart.org/content/liberated-pixel-cup-base-assets-sprites-map-tiles

Kenney
http://opengameart.org/content/platformer-art-complete-pack-often-updated
http://opengameart.org/content/puzzle-game-art
http://opengameart.org/content/space-shooter-art

ansimuz
http://opengameart.org/content/country-side-platform-tiles