If you want to print a poster or banner using a small printer (I use Canon iP1980) in Ubuntu, try Posterazor. To install it, use Synaptic, or Ubuntu Software Center, or type this in Terminal:
$ sudo apt-get install posterazor
How does it work? Posterazor will make a PDF file containing several pieces of a high resolution image (bigger than a Letter/Legal page size). Since it needs more memories, I recommend you to print one page at a time.