Sprays
Sprays are a feature of the PC version of the game by which players can 'spray' their own pictures (Default Key: "T") onto any surface. The image file can be uploaded to your spray list in the multiplayer menu (though note that the image file must be jpg, bmp, tga or vtf). There are several sites that offer a variety of TF2 sprays already converted into vtf format.
Useful gameplay application is almost negligible, though they can sometimes trick the enemy into thinking you have a crouched Sniper, Sentry Gun or have placed Sticky Bombs (from a distance) or in some cases even distract the enemy. (See video)
Sprays can be enabled or disabled in the game's multiplayer options tab, but how many are displayed at once (if any) is dependent on the value that mp_decals is set to. It must be above 300 to show sprays, and the higher the value, the more sprays that can be loaded at once.
