One thing I saw on some browser game a long time ago that I really liked was the concept of a "Daily Dungeon". Each day it was randomized with a new maze like layout and quest to complete while battling tougher monsters in each dungeon level. The deeper you had to go to complete the quest the more experience you earned. If something along this concept could be made, it would give some people a reason to login 'Daily' and try to complete the quest in hopes of a large experience reward. If you could manage to make it randomize around it would be new and different everyday making it a worth while thing to explore everyday.
Now I know Graal is totally different than a little browser game, but I'm sure with Tig's talents something of the sort could be accomplished.