These are wallpapers, are they? If so, create a personal page (if you don't have one already) and upload them. Be sure to include a link to their copyright policy page so that you can prove that you have permission to use the images; otherwise, they will be rejected.
There are some amazing pictures in the NASA gallery; I have about 10,000 of them. They are all in the public domain, so they can legally be used for any purpose.