Has anyone found a finance company that offers low rate financing to customers for upgrades such as home theater systems and lighting upgrades? Before buying an electrical contracting business I owned a John Deere dealership and low rate financing sold a significant amount of product.

Did you check with the store? If not you need to go to your local bank and see what they offer on a home improvement loan.
You will not find to many good deals anymore as the credit crunch is tightend up this form of financing. Depending on what area in the country you live will depend on what your going to find in the way of deals.
My bet is to go to the bank. You get to deduct the intrest on the loan which will help offset the additional intrest fees over the long haul.