If Mark, the admins and participants are agreeable, perhaps the banner/logo that's eventually selected could receive some group input and go through a bit of refinement. Like if the image is perfect but the text too small, or contrast makes the name difficult to read, etc., and if the submitter is agreeable, then maybe a 2nd & possibly 3rd version could be created & the refined variations on that logo could be voted on to get to the final. Might be a pain, but thought I'd toss that out there.
I've actually been worried about a logo that might win that isn't within the size specs, so I know what you mean Jeremy. If that does happen, it will have to be resized before it is put into production. If a logo wins and the submitter is open to tweaking it I don't see any harm in that, especially since it has the potential to make it better. I'm sure the opinions will run the gamut on this idea though. I'm open to any ideas that could possibly improve the final product.