There are five Gatecrash booster packs, so it seems like a safe guess that the five guilds of Gatecrash will be represented. This one is Dimir!
Let's see... this is a big goon of a bruiser, so this is probably Gruul.
It's not immediately clear which guild this image is attached to. So we'll do you a favor: it's Simic!
This image shows an Orzhov mage of some sort.
And finally, an obvious Boros picture. Before we go, here's what a full display of Gatecrash booster packs looks like: