The Image Uploader is a tool for BZFlag map authors. It is to allow map authors to upload textures for use in their maps. Note that:

• BZFlag 2.0.x only allows textures to be downloaded from a limited numbers of hosts, one of these being images.bzflag.org
• BZFlag 2.4.x only allows textures from images.bzflag.org. Some images that had been on various username.bzflag.bz hostnames have been migrated to images.bzflag.org/bz_legacy/username to ease migration to 2.4. Maps will need to be updated, however.

Therefore, by hosting your images here, you can be sure that players on your map can always view it the way it was intended, textures and all. They won't have to edit their downloadaccess.txt file to enable your textures.