I'm not familiar with a "content-bases image retrieval system". Could you explain a little more how this works?
Currently, The Image Gallery feature allows you to create mulutiple galleries and sub-galleries. You can add descriptions to all images you upload and those descriptions are searchable, so that you can locate a particular image by it's description (or also by the name given to the image).
You could if you wanted to create a gallery, one for each user (and allow only each user to upload to his/her own gallery), but still allow other users to search and view images from all the galleries. Is this the type of thing you mean?