Yeah, I've seen all these illustrations. You can see sunhearts in a few of them, but there are a couple illustration descriptions in the audiobook focused only on the sunhearts that don't seem to have an illustration associated with them.
1. "A red Sunheart. It resembles a glowing red and orange gemstone with roughly carved, uneven facets"
2. "A black Sunheart, it's power consumed"
Edit: the coppermind page for sunhearts has both images. It might be good for those images to be on the same page with the rest of the Sunlit Man illustrations, but that's not a change I can make.