Even if you don't want to let (paid?) users access their previous revisions, it's an easy way to have basic undo functionality. You'll get "Help, I deleted my whole work history and don't want to enter it again!" support requests or disappointed users ("I can just hit Ctrl-Z in Word, why do I bother with this?"). Take care of stuff like this in the beginning and it will save you some headache later.

Images as blobs for webapps are generally a bad idea. You can't do a lot with them in databases (browse, analyse, join etc.). There's some overhead if you fetch them from the DB for each request, so they'll end up in some file-based cache anyway. Save that step and just put the path or filename in the DB. Or if you've got one image anyway, just ditch the column and have /img/users/<db_pk>.png.