In C:\Program Files\Autodesk\Textures (or wherever your program is installed) there is a file called ParkingLot.dds. This is the default image. If you move this out of the folder and take the image you want and put it in the folder. Make sure you have the file extensions showing (In Windows Explorer, Tools, Folder Options, View tab, uncheck "Hide extensions for known file types"). Rename this new image ParkingLot.dds. Then test it out. The image may have to be a .bmp, but I'm not sure.