I'm not that familiar with the methods other games use, but most of them seem to either use a set of tiling color textures which are selected per-polygon (though those engines usually don't use LOD, and just have a static mesh for terrain), or texture tiles similar to the tile blocks used to create maps in 2D games.

Personally I think a set of unique textures for the whole map is the way to go (no color texels are repeated), since you can bake your lighting (and other things such as tread/skid marks) into the texture. You may just need to increase the resolution of your unique textures. Also, detail texturing makes a big difference when used with lower resolution color textures.