We did that in the LightWave forum years and years ago [the current mods removed them tho :/ ], a couple times actually I think. If I recall the way it was done over there, was the top three as voted by the community were put into rotation, so that each page load you'd get a random one. Doesn't necessarily have to be a one banner to rule them all situation.

Was a really popular challenge, cause it allowed for smaller, quicker works than most other challenges did, the forum was a lot livelier back then tho.

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