Maybe I'm missing something but I don't see an "archive" option in the latest version of
vB where you can move messages to an archive.
vB has a build-in archive that all posts are added to but that is mainly for spiders to use. If you move a thread from one topic to another in
vB, the link to that thread stays the same and any attachments stay the same.
I also agree that using usernames for the directory structure is not a good idea as one person could have 1000s of pictures. That is why hashing works well, it doesn't matter who uploads it or to what topic, it gets put into a directory depending on it's name.
vB uses a system that does allow you to upload different files with the same name. It also won't let you upload the same file even if it has a different name. Also, their system allows you to put the directory the files are transfered to above the web root for added security. While their system isn't ideal (it puts attachments into directories by user ID), the system they use eliminates a lot of problems and solves many other issues. Put a hashing routine in there for directory placement and it would be close to ideal IMHO.