Hi,
It would be kinda neat to be able to customize aliens.
Not so much the looks of aliens, but why not that too (provide some .gif or .jpg or .png or what not, or if it has to be a 3D model, that could be used too).
Also customize the values of the aliens, and a pre-set of behaviour (sneaky ... aggressive... cautious... swam-mode)
The idea is that a player could customize heavily before starting to play an Alien Invasion game.