If you have a look a the code, there is a whitelist of controls that you can allow to be edited.
This is just the start really, I think being able to change images/CALayers etc can be added in quite easily.
Some written information, even just a general background would be useful.
I live and work in the UK, my designer friend lives on the other side of the world.
Whenever he has a new design for an app I'm making, he sends me the PSD files, I cut them up, export the images, add them into the app, compile and send him a new version of the app. Rinse & Repeat.
This is a crazy way of working. By allowing my designer friend to login to itheme.com, he can create different layouts of my app and test them in realtime.
I can then look at, and try out the different themes.
Thanks
Chris