New alien race ideas - guidelines before starting?

[Destructavator]

One thing I've noticed that could certainly use improvement is more alien races - I've noticed that right now there simply aren't that many, and the galaxy is a big place.  I've had a couple of ideas for alien races and for modeling them in Blender, and I don't know if I'll have time to make them soon but if I do, are there any basic guidelines for scale, dimensions, basic rules/restrictions, etc.?

So far, I've picked up that heads are separate from bodies, and that models are exported in MD2 for the modified quake engine - please correct me if I'm wrong - and that lower poly count is better for rendering speed.

[BTAxis]

Correct, but there's also the problem of animating the model.

[ghosta]

http://ufoai.ninex.info/wiki/index.php/Modelling

[blondandy]

while I agree that we always need more aliens to kill. It is a difficult first project. Also, the more alien types we have, the harder it is to maintain. For example we need walking, crouching, death, crouch walking animations. hopefully, in the future we will also need climbing ladder and lying down animations.

maybe start with an easier modeling task.