One detail which many have found intriguing lately are the thin pink ribbons around the upper left arms of many of the heroes. They can be seen most clearly on Tifa and Cid:
Also, Marlene wears a pink ribbon in her hair:
What is the purpose behind these ribbons? On the messageboard, Kiadria pointed out that the ribbons looked "an awful lot like it might be Aeris' hair ribbon". Diamond Weapon theorized that it might be some symbol to remember Aeris by. It is certainly a logical idea...
UPDATE (August 7, 2005): Adam Ramli has sent in an interesting thought concerning a possible practical use for the pink ribbons. He writes: "Since, in the game, ribbons are used to prevent status ailments, unaffected characters could be wearing them for immunity to Geostigma. I personally don't think it's true; just something to think about." This is especially interesting since we're not sure if Cloud-- who is afflicted with Geostigma-- wears a pink ribbon.