Mister Nifty pointed out Grunge Textures which is a get site to get free backgrounds for your presentations. On top of that they are high enough quality to be useful for print design as well. As they say on their site:We have a growing collection of quality images ready for you to download including Aircraft Aluminum, Asphalt Textures, Brick Textures, Concrete Textures, Drains, Vents, & Grates, Grafetti & Vandalism Textures, Metal Textures, Mud, Clay & Earth, Old Machinery, Paper & Cardboard Textures, Peeling Paint Textures, Rusted Metal Textures, Spills & Splatter Textures, Stone Textures, Trash & Garbage Textures, Wood Textures, and other Distressed Surfaces.
