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.
James Bachini is co-founder and CEO of JSEcoin Ltd, a blockchain startup working to utilize browser based mining to reduce the excessive power consumption of traditional cryptocurrencies.