I admit I always install themes and so on either with the package manager or by hand. This entry on Ubuntu Brainstorm is asking for a program to turn all parts of a given theme on the current computer into one big file so that you can upload it to places, and then also to turn it back into parts of a theme again when people have downloaded it. It sounds like a job which could be done by a fairly simple pygtk application. (I could write it, but I have a lot to maintain already.)
(I didn’t see the Brainstorm post originally, but it has spilled over to various other forums.)
There’s a button for installing themes in the Appearance properties, but right now there’s no “Save As” button to automatically export them into the right format for installing by somebody else. Bit of an oversight, you’d have to say…
There are at least two apps for installing themes and backgrounds directly off of art.gnome.org and I’m fairly certain that one of them already supports this. (I can’t remember the names at the moment, but I can dig them up if you’d like.)
Still, this is a feature that belongs in GNOME’s Appearance dialog and it’s clearly not there.
See https://launchpad.net/epidermis