Of course!
It's an outlet for creativity, and something to think about when I'm on the Metro or in between calls at work (not now, but different times).
I typically have at least one backup concept/game fleshed out enough that I can build it in a few minutes. I typically have a few more that I can take out if necessary, but not to the point where I know what their equipment would be. It helps to actually build them, though, as concepts that appear cool at first blush often aren't quite as cool when built.
Ironically, we've noticed that having the backup character usually means that there is no character death. However, since we too are running Return to the Temple of Elemental Monteism, Punchy*, the warforged fighter/Gladiator, is ready to roll.
Brad
* - I typically assign my concepts relevant project names when working on them. Punchy the warforged, for example, is all about the slam. The Bitey Project involved a disturbing anthropomorphic tyrannosaur, and so on. My current Eberron fighter's project name was "Dwarven Hammer Chick", which is ironic, as she uses axes now.