I have the same problem. I used a transmutation stone to try and use the appearance of my flaming gem stone from my elementalist character creation on a new item and now no art appears for the item at all when I equip it.
Strangely, when I go to the character select screen, it DOES show up, but not once I log back into the game.
I’ve got the exact same problem with my storm eye. It appears in character selection, but when I’m actually playing the game, it won’t show up at all.
Hopefully they get around to fixing this!