Why not just randomize all 8 images with a no-frills PHP random banner script?
They won't rotate in sequential order, but the end result is pretty much the same in that their relative position will always be different with each refresh. It evens out in the long run, and as a matter of fact I think it's a superior method because otherwise if done sequntially, then all those people who only visit once or twice will always be seeing the same ads at the top thus giving them more 'weight' relative to the bottom ones.
Randomizing nullifies this.
Plus the method you describe would require both database support, as well as a fancy system which you mentioned not wanting.
