I know what you mean..I have said more than once in teh last week "I need to join fabrics anonymous!" I work part time at our LQS...adn I can tell you it is more than a job for me..I love just walking in there..I have been spending my pay check in fabric...( I am fortunate to do so) so I usually buy all the latest and greatest fabrics that come in .....only because I like them! It is becoming a sickness! I can't really tell you what I would be looking for because really...the whole thing is so subjective and different things appeal to different people.
I would say for an online shop....you would probably need to offer things in kit form.....Do monthly specials..and monthly blocks...a jelly roll of the month club...something like that?? I don't know ;-)