Hollow-looking, overly-bright eyes go a long way to convey "mad" - dark makeup around the eyes to emphasize the whites and give the impression of hollowness and lack of sleep, and either continue the dark through the socket/underlid or use a slightly bruised-looking color. Make the rest of your face pale, to emphasize the air of uncanniness and to help the dark makeup and eyes pop out more. Something like this:



Artfully smeared but otherwise-perfect shadow or lipstick is another signal of "something isn't right" - it doesn't have to be much, and if overdone it starts to slide into the "kinderwhore" look (and it's easy to over-do) but it can be effective.