You can see other shots of the symbol wherever Karn is depicted, and in many of the cards where Urza is depicted, which is rather a lot throughout the Weatherlight Saga.
Check out the Urza's Legacy art of Blessed Reversal. Karn and Jhoira stand behind Urza, who casts a spell to protect them from a swarm of attacking angels controlled by Radiant. Urza's symbol can be seen on a medallion on his chest.
Urza can be seen magically burning his symbol into the metal surface of an artifact creature in the art of Brand.