I think a really useful feature for a lot of us would be the ability to set a bookmark or place mark in the main gallery that keeps track of where you last browsed. If you browse the main gallery once a day for instance, you could set a bookmark at the first and last gallery item you viewed, and then the next day you can quickly and easily identify all the new gallery items that have been posted since your last visit. It could be something like a page break in the gallery page or different color borders on the thumbnails, etc. Another option would be a gallery that only shows new and or updated gallery items since your last visit.
Right now I keep track of my position in the gallery by keeping a text document on my desktop that I rename to the ID number of the latest gallery item when I was browsing last. If I could just click that gallery item and hit "set a gallery place mark here" instead it would be very convenient.