For the Giants we have:
Ninjini, Hot Head
Tree Rex, Bouncer
And for new the regular sized Skylanders:
Flashwing, Hot Dog
Fright Rider, Shroomboom
Jet-Vac, Pop Fizz
You can check out the full sized photos of the poster to see the reposed originals as well as the LightCore poses. Water+Tech, Earth+Magic, Fire+Undead, Life+Air.
In other Giants news, the full list of Xbox 360 Achievements was recently posted so you can get an idea of what you'll be doing in the final game.