These designs are very good, just to keep everyone on track we are thinking of a drawn island (not painted) but think "aero glass" I like the "light" attitude in the designs so far. Here are two links of screens rendered.
Also remember it is an island, with skyscrapers rising up from the island. It's active and loud. Gotham city on an Island.
Helpful links, (but not the dark background on either):
http://cl.ly/3V2m0l2b440P0S1Q3S39 (but not as childish)
http://cl.ly/442X1C2o1j2t3E321U1D (see the digitized grass in this)
Keep in touch with our stuff too startupisland.tumblr.com