Today I'm going with Frank Frazetta because I want to talk about the best cover composition around. Obviously you can't do this each and every time, and there are so many other very effective designs, but this one, for me, is the strongest. It's the simple triangle composition.
I think these pictures really speak for themselves. The triangle composition is the gift that just keeps on giving! Frazetta used it for arguably most of his covers, and it never, ever gets old. If you really look for it in all of these covers, it couldn't be more obvious, but it works every time.
For it to work best, the triangle can't be broken by any major elements, but if it's too perfect it can become static. Notice how Frazetta outlines a triangle in his compositions, but doesn't completely form the shape in an unbroken way. Except for when he does, but then notice how he uses elements to play against the shape and add visual interest, like in the cover with the guy with the guns and girls. The guns are small enough, and peripheral enough that they can break the composition, and he's angled them in such a way as to frame the main character's face, and slash some movement across the page. That movement stops your eye from simply following the too obvious triange shape.
As a bit of an aside, I can't help but mention Frazetta's use of light and detail in his compositions. Notice how focused his lighting is, with the greatest contrast in his center of interest, and points of light hit on other elements in the picture, just enough to draw your eye across them. He always knew what the focus of his picture was, and he knew how to draw you there, and then lead your eye around to other secondary elements, almost like a visual tour. That's all accomplished through use of focused lighting. No photo reference is going to teach you that one!
The other element I mentioned is detail. Because Frazetta was all about instant visual impact, he was very careful to not detail elements of his pictures that were secondary to that goal. That takes so much discipline....it's much easier to noodle everything in sight! I could learn a thing or two from that...
Anyway, more later.