Firstly, I'd love for the descriptions to parse the <lj user="username"> and <lj comm="communityname"> tags, so that we can include credits and links in the description with the pretty links. As you can see in my current gallery, the html currently just looks bad. This seems like something that might be style-dependent, in which case I could probably edit one of the styles out there to do it, though the one I'm using right now is sadly closed-source.
Secondly, it would be very nice to have a direct link, when viewing other people's galleries, that allows you to upload the picture/thumbnail as a user icon, with defaults of the picture's Title for Keywords and Description for Comments. The current system of copying the image into ones own gallery and going through the "manage picture" page is possibly even slower than just downloading the image and re-uploading it. This, I think, needs to be addressed at a lower level than the styles, though I may be able to hack a temporary method (opening the normal upload form with the web address filled in for the correct-sized thumbnail) in a style. It seems like something that should be pretty basic if you really want to claim "integration" with LJ.
Finally, even if the above isn't implemented, it currently seems that if you go to copy a picture from somebody else's gallery to your own, it doesn't fill in the Title and Description boxes with defaults. Seems to me, the defaults should be whatever the Title and Description of the original picture were.