What is the desk to be used for? It's really to small for most craft projects. The first order of business is to clear it off. Purge what you don't need and organize the remaining stuff.

I put two of these (all wood) IKEA units in my "Babe Cave". They are only 13" deep, but are perfect for everything I have - sewing, needlework, stamping, jewelry making, genealogy, books and more.

You should have just added this pic to your other post. I know this is a girls desk so I will satrt there. All this stuff has to come off , then she needs to figure out what she needs and gets rid of the rest. The cabinet above would be perfect for storing all that stuff in and leaves space for more. My question is since there seems to be no room to do anything on the desk maybe a larger one would be a good idea too. Could you maybe post some pics of the room, this is a good age to start getting her involved in her space and maybe that will help with the mess since you mention that in your other post. I fink kids rooms tend to have a lot of things that they have outgrown too so get her involved.