OK, it can be done. Here's how:
- Open the material editor by pressing M.
- Select the Ink 'n Paint Material by clicking the standard, then Ink 'n Paint from the choices.
- Under the Paint Controls rollout, where it says "lighted," you'll notice theres a choice to select a map which is currently set as none. Open that up and select tiles from the list.
- Test render to make sure you got it. (It might not look like Ink 'n Paint unless you have shadows covering it).
A couple notes. By unchecking the check box under where it says "shaded," you have an option to apply a completely different material using the same technique. Also, you might want to apply a slight bump using the same tile material to make the grout look more realistic.
Attached is the test I did for experimentation. I have the tiles and then just reversed the colors of the tiles for the shadowing and added a slight bump based on the tiles. PM me if you want the file. I'll try to keep it for a couple days. Hope that helps.