Wow Colypso does some great work! My wife is an interior designer and while in school there where individuals who approached the head of the department at the college asking for design work. This became there final portfolio. I would recomending finding a college near by and approaching them with this idea. Think about it would be free and you would have prob 20-40 designs to take ideas from and make them yours.
Many of the larger companies are also having competitions for things like commercials (the super bowl ones for ex.). If the college didnt want to do something directly through them. You might be able to hang signs up in there interior design area and make your own competition out of it. That is a great way for you to get your design and a new interior design student get a real life project.
This doesnt always have to apply to students either. You could run an ad in the paper. Many people would be more than willing to try and design something like that for a prize.
Not sure of the type of business that you are doing but the prize could entail a large gift certificate or a cash prize. The total cost of everything would be alot less than to have a large firm come in and do it for you.