Yesterday I installed Bricks'n'Tiles and it's an amazing program. It allows you to make your own textures for brickwork, masonry and tiles. You choose the image files you want to use, set some parameters, and the program creates a tileable texture.
It's a Windows program, but you can also install it under Ubuntu if you use Wine. First you have to install Wine, then winetricks and using winetricks you install comctl32.ocx and gdiplus.
Hans
PS - these are just some hasty samples to show what is possible
