I felt disappointed with the Sil make-up design. No, I don't mean the "actor's body hidden within a box" approach, I'll give them credit for that. At least they made the box interesting by making it appear to be a tank filled with fluid. No, I mean the way they handled his face. It was just sad, absolutely no attempt to "blend" his features with the headpiece. It looked like one of those "cut-outs" one might see upon a carnival midway; you know, a facade of wood with painted images of cartoonish figures and holes where the faces would exist. You stick your face through the hole and get your photo taken. Past efforts by John Friedlander were far more effective. He's the person who sculpted the original Lynx and Davros masks. It would have been more effective to have hidden more of the face, leaving holes for the eyes and a space for the lower lip and maybe jaw. Greasepaint and strategically sculpted "wrinkles" in the rubber around the mouth gap would have created a more cohesive "whole". Plus, it would have allowed his features to be a tad more "alien".
If that character, or another of his species returned, that would be one design I certainly would not mind being altered and updated.