I see. If this was the case, I would use logic like Zaxo's above to test to see if you need a file, and create a symbolic (or hard) link to the single real default file. This way, at least you've save some disk space, and have the oppurtunity to update to the image in 1 place instead of N.

Using a single image would have additional advantage of being cached in the browser, while having N identical images would mean they all get downloaded to your browser seperately.

Mark