OK, I know this is a big request...
I'd like to see greater separation of the display and the functional code itself.
For example, I'm working in my spare time on some import/export admin tools so people can import/export to/from SWIGS or other similar galleries. It will also enable the creation of static galleries for distribution on CDROM, for example.
The problem is, the functions are not generalized. I will be implementing my own redundant "add picture" routine, my own redundant "create category" and "create album" routines. This will work, but it introduces a maintenance nightmare.
Ideally, those functions could be moved into some of the include files, so there's just a single point that all other fucntions could call.
Developers, I can imagine you're either laughing or cursing if you've read this far. I know how it is. Please don't take this suggestion as criticism of the code you've already written! It's a great program.
This is something that we want to accomplish as well, but all the devs need to become more comfortable with the current code, before re-tooling everything under the hood.