Asp.Net Web application - Graphic Designer

I have developed a web application for a business and currently have completed all the functionality and that is required. I would like graphic designer/ web designer who can take the application and create a nice GUI for the application, including the logo,masterpage, button icons, grid styles......e.t.c NOTE: This is a web application and not a website. My first question how can I do this without giving my code? I would like to see some samples of a web designer . I would prefer someone who has experience in deigning ASP.NET 4.0 Applications. Please feel free to ask any questions ?