NOTE: These are textures in .dds image format, usable in the creation of Sims 3 worlds, with the Create-a-World tool.

What you'll be downloading (should you decide you like any of these textures) are .zip files that contain .dds files. Just extract the .dds files into My Documents\Electronic Arts\The Sims 3 Create A World Tool\UserToolData\SourceTextures. You can also create sub-directories within your SourceTextures directory to help keep your files organized.

Custom Terrain Paints | Custom Road Textures
Game Extracted Terrain Paints | Game Extracted Road Sets