i was considering something like this for xowiki itself, to allow e.g. wikipdeia style names withing the wiki folders (like image:dave.png). From the datamodel is see that parent_ids of item_ids are just acs_objects, therefore, also a forum message should be fine. in some cases it is useful to associate an image (file) with an object, in some cases it is useful to associate it with a folder (in the xowiki case: one might like to use the image in multiple pages, or not to erase it, when the page containing it is removed)... the file selector will only be used when a folder is specified, otherwise the uploaded content could be directly associated with the object_id.... this is certainly interesting to think about this in more detail.
