You can print some of the backgrounds as banners.
For example if you used Dennymfg.com, they require 72dpi and that converts the 12x18inch 300 dpi to come in to 6.25 feet x 4.2 feet, 72 dpi So you can print at 4x6 foot banner. Here is a link to their requirements. http://www.dennymfg.com/InfoBoxDetails.aspx?Id=57ffc92a-5f0e-46dd-9b6e-77a0d40617e4 I saw their products in person and they are very nice.
Another option would be to use the elements from the layered backdrops that you need for your banners and make your own design.
This is the video I did for someone else who wanted a banner that was a certain size and dpi showing how to resize it for a banner. http://screencast.com/t/1K6tKQKmxD
Additional Banner Printing Info: http://support.easydigitals.com/solution/articles/1000112989-printing-banners-recources-and-info
This photo was shared by Lars Thomas and he said: