Be carefully of any contractor that would allow you to supply your own materials. First, the markup on materials isn't that high when you calculate how much time in man hours the contractor will have in actually getting everything and getting it to site, delivered into the basement. Second, most homeowners don't understand that purchasing cheap materials -say saving $5 per gallon on paint will actually cost hundreds of dollars in manpower because of poor coverage.

I like everything except for the rock. It's beige/gold for the floor

Lovely!

While bringing in a designer at the outset it the best scenario, it is not to late to bring in a designer. What do you mean by "it is just an empty room without being designed"? No right or wrong answer. Just wondering what your expectation are. Were you looking for more details in the trim? Wondering what furniture to buy and how to place it? Decor? Hiring an interior designer does not have to break the bank. As a matter of fact, the right one can save you in terms of not making bad decisions. Even if you hire for just a floor plan, you are ahead of the game. How can I help?