Showroom size and content should be determined by the business plan that you formulate for your showroom. You should have a plan tailored to the customer segment you are trying to reach. So it follows that you'll also need to determine the product mix that will get you there.
Indiscriminately adding samples on a whim (because they were free, for example) only adds clutter and creates confusion for both the customer and your staff. Having too many samples from which to choose fosters an attitude often referred to as "option anxiety." You need to have a focused plan to reach your goals!