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I wanted fast access to my python shell, so I locked it to the launcher, but the icon is just a question mark, which I assume means it doesn't have the necessary file. For the sake of aesthetics, I would like to give it one, but I can't figure out how to. That is, I don't know what directory I should put it in, what type it should be (though I suspect .png) or what size (will it resize an oversized image to fit? or crop? or just mess up my dock?).