This script will take up to 6 colours chosen by the user and create a tiled image by choosing a colour for each tile based on a percentage value entered by the user. The percentages for each colour determine the percent of tiles in the image that will use that colour. The colour and brush to use for the grout can also be chosen, along with the width and height of the image and the width and height of the tiles themselves.
Check out the README.txt for more info.
Comments and any useful info are welcome since this is my first attempt at a script.
If anyone wants to modify the script then they are more than welcome to do so.
 updated the script to v2 based on comments from RobA. The changes only affect the tile grout which is now much faster at being drawn.