Easy geotagging interface. Something like in picasaweb would be very handy: select an album for geotagging. Map is displayed, and all pictures in album listed as small thumbnails. Pictures already on map are marked with a watermark. User can drag a picture on map and move it around. User can remove a picture from map by dragging it off.
In general: when having more than 100 pictures the admin existing UI is very hard to use.