Myself, I post images to a private thread containing just me, and use those for the guides. Though I have plans on adding file attachments to guides (which would be enabled by the "Forum Uploads" package).
Thanks for the thoughts Chops.. I don't like the idea of having the guide images attached to a user's post.. If I one day ever want to delete USERX from the system entirely, including USERX's post, the guide will go boom.
The gallery idea would work. But your idea is the best. Until that low priority feature is implemented, I can just tell people to upload images to the guide gallery.