Wow I don’t mind admitting half of these companies I’ve never heard of before: Display marketing infographic (from http://www.lumapartners.com a good blog actually looking at the industry from an investment perspective) They also have ones for mobile, social and search: http://www.lumapartners.com/lumascapes/mobile-lumascape/ http://www.lumapartners.com/lumascapes/social-lumascape/ http://www.lumapartners.com/lumascapes/search-lumascape/ and my favourite, just in case anyones working on the next MyFace: http://www.lumapartners.com/lumascapes/digital-capital-lumascape/
Here are a few ideas for split testing your banner ads. You could quite easily use these to take a single ad and knock up a 100 variations. Test them optimise out the losers and see what works best. There is no single best banner advertisement, everything needs testing and optimising continuously.