The Zohar (and Megillah 28a thanks DoubleAA) says that it is Assur to gaze at the face of a Rasha. Would this also apply to looking at an image or painting of a Rasha?
First of all, it should be clarified that rasha means wicked person (technically just wicked, but it is a substantive ). And asur (assur) means forbidden.
As Rabbi Yochanan says (Megillah 28a), it is forbidden for a man to gaze at the "tzelem demus" of a wicked man...
Tzelem means image, and demus means likeness. Rabbi Yehoshua ben Korchah said that he never stared at the tzelem of a wicked man (mentions nothing about demus). The gemara then quotes Rabbi Yochanan (see above).
So, I would think that Rabbi Yehoshua ben Korchah was saying he never looked at the actual face of a wicked person, based on the Rabbi Yochanan's teaching that even the image of his face is forbidden to stare at.
On a related note, when I was learning from Rabbi Shamai Warman (a teacher of mine), ShLIT"A, he taught us that it is a good thing to look at the face of a tzaddik (righteous person). If I recall correctly, according to Midrash, Yoseph saw the face of his father Yaakov when he was secluded with Potiphar's wife, and it was on account of having the image of the tzaddik embedded in his mind then that he fled from her. Something to think about.
Anyway, it is probably really bad for the soul to stare at pictures of people like Hitler or Bin Laden. That is probably what the Talmud in Tractate Megillah was referring to, if I understood it correctly.