I have been looking for a solution to enable sorting on multiple images uploaded via UploadField.
Sadly this didn't seem to exist (or I'm just too stupid to search properly?).
I wrote a small extension to the UploadField that adds sorting functionality to has_many relations. Download and instructions can be found here: https://github.com/bummzack/sortablefile
The implementation is still very basic. There's not much error-checking going on.. so if you encounter issues, please post them on github.
Hopefully this turns out to be useful for somebody... enjoy.