You know the diamond-shaped dragon that is on the cover of Morrowind, on the doors in the Imperial City, etc.? Does that represent Talos, Imperials, Tamriel as a whole, or what? Also, does it have a specific name? Thanks.

I always assumed it was Akatosh, and that it symbolised the rigidity of time.

It is the Red Diamond, a symbol of Empire Actual, the Septim line, and the dominion of Akatosh in general.

The Diamond symbol dates back to the time of Alessia, long predating any use of dragon symbolism in Cyrodiil. It's commonly believed to be symbolic of the Amulet of Kings, believed to have been given to Alessia by Akatosh. It decorates the armor and weapons of Pelinal Whitestrake, one of the key figures of that conflict. The symbolism appears before the Alessian forces took White Gold Tower, which the Amulet is the stone for. While I suppose it is possible that the Amulet belonged to the Ayleids originally, there is no known Ayleid symbolism alluding to the Red Diamond.

The Dragon symbol represents Akatosh, a symbolism that came about as a result of the Akaviri invasion and later peaceful co-existence with the Imperials in the late First Era.

There was sometime a theory about Akaviri origins (or at least influences) of this symbol, but now its status is uncertain, I think - it is possible that akaviririans adopted dragon symbolism in Tamriel, and their "enslaving of the Red Dragons" just a metaphor of Potentate period...

For the Ayleid it was more of a bird thing then a dragon thing, there are some statues showing what appears to be Auri-El transforming into one in his escape from Mundus.

As for the first association between dragons and Cyrodiil. With the Alessian pantheon being an amalgam of the Nordic where Alduin is a dragon and Altmer/Ayleid pantheons where Auri-El is a bird or man you'd end up with Akatosh as a dragon man - and what else is a dragon but a fire bird? Alessia being the High Priest of Auri-El | Akatosh and the amulet being the symbol of the her right to rule in his name means that the diamond and dragon symbolism were present at the start.

I also recall some references to Auri-El as being a Dragon. Can't find those right now.

The dragon symbolizes the obstacle on the hero's journey. Anyone foolish enough, to associate themselves with the dragon, will meet the moon, on a giant, impaling stick.