Show me a picture

um one of B.E.A.S.T. has a fantastic metal cut out

The Holy Symbol of the Fire Dragon is shown in the Player’s Guide to Arcanis from the 3.5 campaign. It’s on page 61 of the 2nd Ed. It’s a little hard to describe, sorry.
Also in Ssethregore: In the Coils of the Serpent Empire on pg 44 in the story of Ven val’Sosi when he is in front of the altar, it describes the modern symbol of the Fire Dragon being a flaming circle.

The Fire Dragon is depicted in one place but it is described multiple times. In Ssethregore: In the Coils of the Serpent Empire. The Fire Dragon is described as being a Great Fiery Wyrm in 3 places. In the story of Ven (pg 44), in the description of Black Talon’s arrival to Lanpeltis (pg 46) and the city stats of Lanpeltis on pg 31.

Kassegore is also depicted once to players. He is described as being a very large ss’ressen. There is a module from the 3.5 campaign that take place in a joint temple of the Kassegore and Yig (Wrong Turn at Coryan.) You see this depiction of Kassegore with a giant amulet with the Fire Dragon’s symbol on it, so any Black Talon that played it could learn some uncomfortable truths if they put the pieces together.