The Special:Upload form is "redesigned" by taking advantage of the "uselang hack". All the MediaWiki messages that appear on Special:Upload have alternate versions created at (e.g.) MediaWiki:Uploadtext/foo and then users can use that version of the form by going to index.php?title=Special:Upload&uselang=foo.
This method has been used successfully on at least Wikimedia Commons and English Wikipedia, but on some wikis, the MediaWiki:Licenses/foo gets ignored and only the default MediaWiki:Licenses gets used. (This message is the list of license options that appears in the drop down box.)
This problem has been reported to me by the Greek Wikipedia and Citizendium wikis:
Apparently also http://en.citizendium.org/wiki/CZ:Upload-Wizard but you'd have to beg for an account to confirm. ;)