I have a Cubit "Cubits Themes and Header Pictures Forum" about how to make banners with your own pictures. I do recommend Zany as well. I visit her Cubit pretty often. She can help with a lot more than just the banner pictures too.
Another one is Evey`s Blissful Banners. She is a talented artist who has helped people make some beautiful banners.
I have not done a lot on the banners, just touched on them a bit here and there. I am always happy to help. But for the best help on customizing Banners and themes Karen's http://cubits.org/cubitthemes/ can't be beat!