Wonder! Science! Mystery Men! The Blue Beetle!
Comic book covers tend to be designed to get people to pick them up and buy them on impulse. If you think of your primary audience as being familiar with the characters, for instance, having an apparently dead hero on the cover is usually a good selling point. If, on the other hand, you’re just trying to convey “Action and Adventure Await,” I don’t think you can do much better than these covers from 1939-1942 Fox Comics. 
Link courtesy of Scott Saavedra’s Comic Book Heaven
