Here's a couple of sites with tutorials on making seamless tiles, for texturing your models:

http://graphicssoft.about.com/library/weekly/aa080499p2.htm
http://www.cadtutor.net/tutorials/photoshop/seamless-tiles.php
http://www.sketchpad.net/tiling2.htm

These tutorials are mainly dealing with coloured tiles, but the same techniques can be applied to you own black and white tiles if you want to have seamless textures on your models. Remember to save your textures as 512 x 512 pixel ".tga" files.