I think it should be doable, I have played with php a bit.

The image when is posted I assume is linked to the user. So the image in physically is stored attached to the user. All you would need is an additional field for the listing, or change the xisting listing field to take into account multiple listings.

like this:
name:            author:         listings:
image1.jpg   bloke1         sci-fi, comics, fantasy

Then the php scripting should be able to split the listings and display the output accordingly.

But doing this would throw other information architecture problems. For example on the front page of the galleries you would get multiple links to different galleries for each image. Maybe the idea would be to change the listing to a more "flickr" type of listing with tags instead of listings, but then if you do that you have to completely change the way the listings work, etc, etc.

Not triying to scrap the idea, but I have worked in these types of projects and I can tell you that it would take some work, and more than just the mechanics behind the scenes.

===========================================================
-'I curse the day my curiosity led me to investigate the strange stain inside
the atomic acelerator chamber'-
The Nuked Bug