This reminds me of some freeware application I saw a long time back and wish I'd bookmarked - it takes an image, hand drawing, whatever... and you pick the tile size (1"x1", 4"x4", etc.) and it converts to a template for you to layout the picture using tiles. Argh... it would be so easy to take a screenshot of Galaga or other, remove the black background using a graphics program and convert the remaining image to a tile template.
I'll do some digging and see if I can find it again. (I found it originally because I was looking for tile templates for a back patio area.)
Jim