OK, I'm assuming you're using Poser 4. You need a 2D program (photoshop, Paint Shop Pro, etc...). Make a white square and put a black grid on it (better use 2 layers). If you want your tiles not to be too sharp, apply a small amount of blur to the black grid. Save as JPEG or TIF. Use this map as a bump map (Poser 4 will ask you if you want to convert it to bump map, say yes). This will give the look of a tiled floor. Re open the original black on white grid (the Photoshop or Paint Shop pro one) and paint the white squares with something you like (or better still, paint the whole white layer, then put back the black grid on it). Save as JPEG. Use this one for the texture of your ground. If you're using Poser 5, it's even more simple : open the material editor and chose "tile" for your texture. Any image you'll load in will repear itself over the ground (provided the image is not too big for the ground, but that can be fixed with the "scale" parameter).