Below is a template for an interior design services contract. It's important to complete the Project Time Estimate System worksheets before you create your Letter of Agreement.These two tools are meant to. A proposal is a detailed project document that defines the scope of work, the process, the schedule, and the total price (usually in the form of a fixed fee). Use this interior design contract template as a binding agreement for clients for your interior design services. Shel Perkins offers a sample independent contractor agreement that you can use when subcontracting with design firms and ad agencies.