Code Gurus, please help!

I have created some graphics for different days of the week and I would like to be able to get a script going which will place those graphics as a header to a post on the relevant days of the week. For example, a post made on Monday would automatically have the graphic for Monday as a header image. I’m thinking it should only take a simple PHP script but alas, it’s beyond me. I’m hoping someone will be able to help me, pretty please!

I hope I’ve described it well enough. Reading back it sounds a bit tacky but rest be assured, the graphics are tastefully done and fit in with the rest of my site! I would post a link but I’m afraid I’m just working on it on a local machine at the moment. Any help would be greatly appreciated.