The Metal Blade tent gives you a free pack of bookmarks, by the way. They're all with band logos (Red Fang, Clutch, All Shall Perish, JFAC, Red Chord, 3IOB, Chimaira, and more), and the Roadrunner tent will give you a Machine Head lithograph signed by the band if you pre-order the album. If something pretty signed is what you want, save your money and get a free Machine Head poster when you come to Machine Head's autograph session. For those who want to meet Trivium, you've got to pre-order it or else it's a no-go. They give you a bracelet and if you don't have it when you get in line for the signings, they'll throw you out.
Also, the vendors at the official Mayhem merch table are complete dicks.