Hi!
I would very appreciate to have some group ACL.
Think you have some party pictures, some very cool party-pictures and "normal" pictures.
There should be a group "relatives" which you can define to only access the "nomal" photos, and some other groups like friends1 and friends2 and whatever.
This would make permission setting a much easier task.
rgds
Luc
PS: gallery is very cool stuff!