I need some sort of illustration to symbolize the idea of two-fisted action SF adventures on alien planets, but it needs to be out of copyright and not too inappropriate for 1930s SF. I think that the sort of thing I need is a man, a woman, a rocket, and some sort of alien beastie dying horribly as they zap it with ray guns.
Another possibility is something expressing dramatic tension, e.g. this still from the 1930 SF musical Just Imagine:
But it's all too easy to give it a very slashy interpretation.