Some people attach images in their questions, even if these don't add any value in helping others to answer the question (example). Should these be edited?
I agree with Tylershads, if it’s nothing but hindering the question, remove it. However, in this particular instance I think it serves as a reminder of what The Joker’s makeup looked like, so it’s an ok image to have with the question. If it had just been a random picture from the movie that didn’t include the Joker then I could see removing or replacing it.
In general, I don't see a reason to edit the images out.
However, if they are completely off-topic pictures, for example, a picture of My Little Pony on a Matrix question, by all means edit out as it clearly does not belong. Also, if the question is rampant with pictures (read: 7 where only 1 is really needed) then again, feel free. But there is nothing wrong with a little visual aid of a scene, character and the such.