Here's over 3800 free tiling textures.

They are shown already tiled.

Download whatever ones you like. They are freeware.

Skybox Ground Tiles from the old skybox site
Textures part 4
Textures part 3 (even more tiles)
Textures part 2 (hundreds of tiles)
Textures part 1 (hundreds of tiles)
Textures Botanical (tiles from botanical photos)
Toke Tile Textures (tiles with a marijuana theme)
Animated Textures
Rock055 (variations of the freeware texture rock055)
ActiveWorlds section has many transparent gif files of plants and tiling vines.