You will find a lot of images that can be used in your games at the following links:
http://opengameart.org: This site provides free 2D and 3D art, concept art, and textures that can be used in our games.
http://www.rpg-palace.com: If you are developing an RPG game, this is your place. Here, you will find free characters, scenarios, and other related resources to create your game.
http://untamed.wild-refuge.net/rmxpresources.php?characters: Like the previous site, you will find a variety of free resources for your RPG games here.
http://www.textures.com: This place is recommended if you wish to find a wide variety of free textures that you can use in your games.
http://www.spiralgraphics.biz/packs/browse.htm: This is yet another complete site that can be used to find high-quality and free textures.
http://www.pixelresort.com/blog/app-icon-template: This site offers a template to generate all the icons for your game, which can be uploaded to the App Store.