As a brush, it can't be done (unless the colors you want to preserve are grayscale...for that just increase the brush spacing). If you want color then you could open the color image, copy it, paste in the map, then make a whole lot of duplicates of that layer and then move them around. Usually that's not worth the effort. What most folks do is use GIMP or Paint Shop Pro as they do support the sort of thing that you're looking for...it's called an image tube or image hose.