Methinks you may need to clarify what you mean by "rotating". It could mean an animation making it look like it is rotating around an axis, or it could mean that you rotate through several distinct banners over some periodicity (like a "pitching rotation" in baseball as opposed to a rotating curveball in baseball ) which may be what the first couple replies were addressing.
If what you need is an animation effect, then it is going to have to be something that runs on the client side. I would think an animated GIF would be the simplest and most portable solution. However, from a style viewpoint, I would attempt to dissuade the customer from this, as many people (including yours truly) find such things to be annoying and generally tacky.