I like the theme days idea. Make sure it's obvious somehow to customers. I think incentives can help sell things.
I think all you can do to sell items is to put them on people's faces, chat them up, and hope for the best.
For morale, make sure to praise as much as possible and put positive spins on the negatives. Like if you're under what you should be, tell people that what they've done is fantastic and that you know that they can reach whatever the goal is, because it isn't that much more. Don't talk down to them, but be supportive.
If you're looking for group morale, why not do some after work bonding or try to get to know each other during meetings, if you have those? Nothing too cheesy in terms of "ice breakers" but allowing each other to talk and have some sort of communication, even if it's just about raising sales.