Just to avoid spamming the thread with lots of huge pics, I'm just going to send you over to my Trek art gallery
, where you can see Jude Law, Claire Danes, Katee Sackhoff, Gina Torres and Marc Warren as various Trek aliens (these were manips done for RPG characters).
Jude Law is an Andorian chan, Katee Sackhoff is a shen, Warren is a thaan, Danes is a zhen, and Gina Torres is a Klingon.
Conan O'Brien would look good as an Andorian.
Some people who could play Ferengis (yep, shortness is a prerequisite
David Patrick Kelly
Charles Martin Smith
Michael J. Pollard
here's how I cast them all in the fantasy DS9 recasting thread