It would be nice to be able to have a single image in multiple categories. So that you don't need to upload the pictures multiple times to get them in different galleries.
I'll try to give an example:
pic 1 has me, Carl and Dave on it
pic 2 has me and Dave on it
pic 3 has Carl and Dave on it
gallery 1 : "Meeting with Carl and Dave" contains pics 1,2 and 3
gallery 2 : "Me" contains pic 1 and 2
This is a simple example but I think you get the point (if not just tell me what is unclear and I'll try to clear that up

)
This would allow me to post the pictures per event and have a couple of galleries in which my friends can find their own pictures.
So I basically need to link one physical file the multiple (sub)galleries.