Here's a lot of free tiling textures.

They are shown already tiled.
Download whatever ones you like. They are freeware.

Skybox Ground Tiles from my 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)
Rock055 (variations of the freeware texture rock055)
ActiveWorlds section has many transparent gif files of plants, tiling vines and tiling animations.