Board Thread:Player Suggestions/@comment-26293086-20150505201300/@comment-26440657-20171025133430

It's funny how there are people who can't see the skull and bones. I took the liberty of uploading the high-resolution version of the raw background image just so people can see it clearly. There's definitely a skull (on the left) and a rib cage (on the right).

As for the theories, I don't really care much about arguing for which is the better speculation. It's a big monster that died and is seen in the background, that's the only fact here. It's possible Terraria spriters just popped it in the background to make the Crimson creepier, maybe as an explanation for where all of the blood and gore in the biome are from.