Design banners for slideshow and promotions for website

Hi, We are currently building a new website and need a designer to work on an hourly basis for an ongoing period. We need some designs for slideshows and promotions that our web designer can upload to our site. We will provide the content for the design but we need you to put it into an attractive and professional looking design. At first we would require around 20 slideshow pictures, plus some smaller style banners to link to promotions on our site. Some of the designs will be provided from our suppliers and you would have to take the supplied design and convert it into a design that suits our site. For example a supplier may provide a design that is 900x300px and we need it to be maybe 750 x 350px to fit our slideshow. In those cases you would simply use the design provided and just change the layout and size. This project will be ongoing as we will need regular (monthly??) updates on our designs. Some of the designs will be permanent and others will change as our promotions change. We need the designer to be able to provide new designs very quickly, perhaps overnight from when we request a new design so that we get maximum impact for our promotion period. Thanks for your interest.