Paladin said:
The "dice in a bag" idea is absolutely great!!! Any other suggestions? We'll take all we can get. Also, why "munchkin"? -Paladinwife
I'd talk to the folks at Chessex and Koplow (dice companies) ... maybe you can get a cross-promotion going ... buy a bag, get X% off dice ... buy Z worth of dice, get Y% off a bag.
Consider the player base there: D&D, Vampire, Gurps, and Werewolf. Make sure you have bags suitable for those groups (black and red would probably be very popular with the Vampire players).
Maybe talk to White Wolf about using some of their Vampire or Werewolf clan logos/names on your bags? I'd suggest the same thing with WotC for holding tokens but they probably wouldn't go for it ... but there's no reason you couldn't embroider a generic flame, tree, skull, water drop, and sun on red, green, black, blue, and white bags....
As for other things to put on the bags: class names (include a few prestige classes), race names, "Monsters," "lucky dice," "guaranteed to crit," "candy" (for those who want their candy in a different bag and don't want to risk accidentally eating dice).
It might be cool if the bag-within-a-bag was big enough to hold a miniature, too. For people who play the same character several times at a show (like the RPGA Living campaigns) that would be handy.
Ask the RPGA if you can put "RPGA" on some of them and sell them at the show.
Definetely talk to Chris Pramas of Green Ronin. I did give him one of those bags at the show last year like you asked me to.
Talk to WizKids and see if they want to cross-promote a fig-in-a-bag.
If you do KODT bags, make sure your ass is covered legally with Kenzer. They're all a bunch of bloodsucking lawyers.

(That's a mangled quote from
The Money Pit, before anyone gets huffy.)
The sew-in label should be fine for the d20 logo issue ... you'd be fully compliant with the requirements of the licence. Then again, IANAL.
For decorating the booth, ask what sort of walls you'll have. You might want to bring a sectional bulletin board and display a bunch of bags on that in the back of the booth, high up so it's visible from across the aisle. Or if it's just draping, bring a lot of safety pins and pin up the bags all over it.
Definitely bring business cards with web addresses.