Steel Ball Run manga covers typically have a bold color palette and detailed background elements that add to the atmosphere. They also sometimes hint at key plot points or themes of the story.
They're popular because they combine the fun of comics, the visual appeal of animation, and the shareability of memes. It's a perfect combo for catching people's attention.
Well, it could be that Edgar is the artist who made the cut cartoon. Or perhaps Edgar just loves and collects cut cartoons. Hard to say exactly without more context.