In the Links you could leave it whole or split it into Writing Helper sites, Publisher Sites and even Member Offsite Galleries
In the Gallery, Since it would be member created art you could do many sub folders but it would be best to leave that open until there were enough submissions to warrant a sub folder. You would want to allow for Jpeg and Bmp or Gif. I don't know about Tiff because they tend to be BIG I believe. Some sub-folder ideas could be 'cifi', 'fantasy', worlds, creatures, ships, maps, weapons ....