Yeah I have this strange fetish for tanks that aren't rectangular. Probably, simply becuse something like that screams "Custom". A huge circular tank would probably be "uber cool" though it would unfortunately also be "uber expensive".
Something else that might be neat would be a collection of cube tanks, each with thier own theme. Something like 3 rows of 3 arranged in a square with the center one raised up higher than the others for viewing. Or all the tanks could be arranged at slightly different heights for a real funky look. You could do 20"X20"X20" (roughly 34.5 gallons each) without having to go with super thick glass (9mm or 3/8 mght work) but then you will need to buy probably 3 times as much of it. Something like that could be adapted an infinite number of ways though.
It sounds like you have vision for your area though. It should look good whichever direction you go with it. Just be sure to share pics when you're done so others can drool.