Don't forget that any upload does get held for approval and since it is done by humans, there will be some lag time as the folks behind this site don't live here 24/7 (I think they are all US based).
That said, if you are uploading purely to archive your UI for personal use, then WoWInterface would not be a good location for your needs. Instead, if you are looking for an online archive, head over to Dropbox where you can get a free 2 GB of space. If you complete some tasks (such as taking a tour, referring others, etc), you get more space. I use it and I find it's quite handy. I also have a utility that integrates into my Linux Home folder where I can just drop files in a Dropbox folder and those file are automatically uploaded (and synched) with my Dropbox account online. This utility works with Linux, Windows, and Mac OS X
Here are two links. Link 1 is a basic link, Link 2 is a referral link for me (I get more space, 250 MB per referral, if you use it). Pick your link, the end result for you would be same:.
Link 1 (basic)
https://www.dropbox.com/
Link 2 (referral)
https://www.dropbox.com/referrals/NTM2MzEwNTE5
If you don't want use the "cloud" route, then the already mentioned USB thumb drive or CD-R works nicely. Again, I keep a USB thumb drive handy with settings, documents and such. They are small, cheap and have lots of space. Some are big enough to cram your entire WoW folder into. You may want to look into that if you got the spare funds as recovering WoW from an archived copy is MUCH FASTER than doing a install/patch/set-up your UI.