I remember there was a Sky UI mod.It completely changes the User Interface.So modding the user interface is possible.The question is HOW?
Do I need Photoshop and Blender for this or is it possible to do through Creation Kit?
I checked out Creation Kit.com but I don't see any tutorial for modding User Interfaces.I'm planning to make a new interface for my game.Any link to a tutorial will be helpful.Or at least point me in the right direction

The UI was created with Adobe Flash Actionscript - so you'd need to be able to code your new menus in actionscript.

You would also need Adobe proprietary software to edit / create some of the file formats required ( graphics / sound / anim )

I think IIRC one of the SkyUI team had the necessary software, but was either unavailable after the files were finished or un-willing to do more .. Hence why there will be no more variations of the look of SkyUI ( maybe wrong in the detail about this but thats the impression I got when asking about if it was possible to have a look similar to DarnUI )

I have not checked for a while, but there was open source software being developed, how far that has come along since I dont know .. Lost interest and got too busy to do anything. If you look into the file formats you are going to need to work with, then google search for editing those formats with open source software, you will find the development topics.

Edit : Also reference Jackstarrs post - I think he is right in mentioning actionscript as the api language you would need to be familiar with ; The newer actionsource api which adobe flash has been using for a few years now was not adopted by the games UI.