the biggest problem I find with this is that files move or get deleted. It is a lovely idea in principle but you may well end up with file errors/unknown file when something gets moved/deleted.
Personally I think it's much nicer to upload a copy onto the website's host (I make sure it is also then resized to a user-friendly size so that displaying it does not kill bandwidth!) as you guarantee it being there in future. But then I have unlimited host space...whereas others may not!
Tough call. the poll needs a "maybe.....write your ideas below" option!
(P.S. I would advise a new area in the brainstorming for POLLS, either that or "stick" the poll threads to the top of the forum - you want as many people as possible to see these polls as quickly as possible so you get a valid idea of people's reactions!)