A link, probably at the bottom and top right of the galleries, for how many pictures will be shown on one page. User defined, remembered via cookie and/or logged in user settings. ex.
[10] [25] [50] [100] [ALL]
Click on one and you view that many thumbnails per page.
All being the especially important one. I hate browsing through 10 pages of pictures when I'm on cable and could easily view the thumbnails of 200 or so of them in a few seconds.
TBH, I'd be surprized if this hadn't already been suggested somewhere in the 800+ other suggested features, but after a search, I couldn't find it, so here it is...