Image Organizer and Move Option
I suppose this can go into plugins, but until plugins arrive on Linux and there's some documentation on how to make plugins, it remains as a feature to hope for.
I could really use a way to organize large collections of images into directories. I've seen this done in another (sadly MUCH slower) image viewer similar to bookmarks. In essence, you add a bunch of various directories from different locations to a list in a side-bar. You click on any one of the directories in the side-bar and the image you're viewing is moved to that directory. I would do this with drag and drop from the image list, but it only copies and there is no option to move instead of copy (another useful feature). It's also a bit difficult looking at many different directory listings from throughout my computer, so a smaller list would work better.