What OS is your server? Why don't you just link to a static image, but setup a cron job changing what that static image is every 1, 2, 4, 5, 10 minuts, or whatever. Whenever your peak time is for the day, you could charge a premium to whomever wants to advertise more during that time, just like TV!
If you want code for this, let me know, it'd be *super* complicated
-scheides
ps--cache-crazy browsers such as IE might not load the current version of the image right away, but would realize it after a few clicks/page reloads.
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