I have my email client set up to play a cash register sound every time an order goes through. It sounds dumb, but it never gets old.
Seriously though, it would be awesome if you all of a sudden you had a surge of sales and your computer made as much noise as a slot machine hitting a jackpot.
There are 5 transaction types and I use a slot machine, cash register, bells, and crowd cheering noises.
Got the idea from this movie http://www.imdb.com/title/tt1251757/
http://www.businessinsider.com/amazon-billionaire-jeff-bezos...