Kind of skimmed this thread...but I might be able to help out with a portion of the project
I have a banner for every single game for the Xbox1 & Xbox360:
Xbox1: 1,000~ Banners (Wide Icons) for every single game. They are all the same dimensions... As well as Arade Banners (Nintendo/Sega/etc), here are a couple of examples:
http://pics.apartment808.com/users/NineT9mustang/MyPrograms.png
http://pics.apartment808.com/users/NineT9mustang/Fifa.jpg
Xbox360: 500+ Banners for the Xbox360... All the same dimensions as the banners above.
I'm pretty lazy and not too active here in the forums, so give me a PM if this would be of interest and Ill upload it to you...