This season of D&D Encounters, Hoard of the Dragon Queen, has a bunch of Dragons in it. Here is my custom paint of the first one Lennithon. And a quick background on my thinking of the Three Adventure Themes:
1. Evolution
2. Escape
3. Mana
I am changing the Dragons a lot at the table.
Basically, the Cult of the Dragon [who have always been obsessed with Dracoliches] are trying to bring back Tiamet & I plan to build on the themes of metamorphism & evolution which are occurring within the Cult of the Dragons objectives--and also with Tiamet herself.
Specifically, I am looking to have the Dragons in the adventure be slightly different than normal--for example, Lennithon is a Blue Dragon in the Adventure, but I have made her a Blue/Black Dragon who has been transformed by the spell plague or something similar. She is bored and she is bruised [black and blue--get it?]. Other Dragons & members of the Cult of the Dragon will be similarly modified...
Escape
Another Tiamet related theme that I plan to build on is Escape--in her case from the First Level of Hell, but in the story I am not really sure how I am going to apply this.
Lennithon is trying to escape her responsibility of helping with the attack, but I think other NPC's embody this theme more clearly.
Mana
And the third theme, that I am still researching, is the idea that the Five Heads of Tiamet are the same colors as the Magic: The Gathering Color Pie [White, Black, Blue, Red, & Green] which I plan to introduce some how as well...