A couple thousand of the same image one one page.

I'm looking for an easy way to put about 50,000 of the same image on one page. I know its easy just to copy and paste the image code, but it gets sort of hard to keep count when you have such a big number. I also plan to change the one image to another image. Anyone know an easy way to manage this. I'll just give an example of what I'm trying to do. Say 50000 stop lights all red. When the time comes I want to change some to green and leave the rest red.