Just like Wurt, his skin has nothing to do with nightmare fuel or shadows outside of it being a "dark/creepy skin".
Every other triumphant skin follows an obvious motif, deep black, with lots of spiked points or curls, with white lines running through, typical shadow related stuff. WX being a slight exception, but his general design follows still follows the pattern well considering his VERY different design from the rest of the regular cast.
But Wormwood and Wurts skins don't follow this motif at all, they don't look like they are influenced by the fuel at all.
You can look at every other skin in the bunch and immediately recognize that they are a matching set, but I seriously doubt anyone could do the same for Wurt and Wormwood if they weren't aware of what "The Triumphant" skins were.
I hereby petition that the name should be changed to preserve lore and consistency.