They all look great! Is there any way to make them the same size? The Johto one is probably the closest to the perfect size, but anywhere between Johto and Sinnoh size would be fine.
I love the placement of the Pokemon, but not necessarily the Pokemon themselves, if you catch my drift. If possible, could you change Kanto's Pokemon to Charmander or Magikarp, Johto's Pokemon to Totodile or Larvitar, Hoenn's Pokemon to Treecko or Bagon, you can leave Infernape on Sinnoh, unless you think Chimchar would look better, Scraggy or Archen on Unova, and Dratini on the Dream World. I tried to make them all first stage Pokemon, so it would be easier for you to fit them in the banner.
I completely understand if this is too much to ask of you, especially after you made these look so awesome. Just tell me if it is.