Help allowing users to add pictures to admin account only?

Hi,I am playing with this great program. I got everything all set up but I am looking to allow users to add pictures to admin account only. I want to do this because I do not want a bunch of branches going in different directions. I would like all the images in one location. I am making a theme gallery for a specific type of phone and I would like to allow users to upload there theme pictures and post a link to the download location. I am not going to host any of the files I would just like to be able to view all of the themes together. Thanks for any help.