Anyone know a good image Ad rotator?

Hi, I’m looking to have about 12 box image ads on my site. 3 across, 4 down. I want them to randomly display in no order when the site is loaded each time. So some can be at the top, then bottom etc. Once clicked, it opens the site in a new window.

I was wondering if anyone knew of a plugin that would do this and allow me to insert it into a page? All I seem to be able to find or banner ad plugins and single images that transition to other images.

This will be a bunch of different images positioned on a page. Ideally I will be able to add and take them away as I like.

Thanks in advance for your help.
Dave.