Attached Link: http://www.buildaposter.com/

You should render it up to the size you want in Bryce first. Depending on the print resolution you want, ie; 300 dpi, 200 dpi, 150dpi, etc..., calculate how many inches you want the poster to be and multiply the inches by the resolution you want. For example at 300 dpi (dots per inch) a 36"x24" poster will need to be 10,800 x 7200 pixels. This may be a bit large and take a long time to render, so let's say you print at 150 dpi, now you're looking at 5400 x 3750 pixels, much more managable. Depending on the printing process, ie: Duratran, Fiery, etc...the printer may have their own requirements of file type and size. It is always best to check with the printer first to see what res. they can work with. You can check with the guys at this link to see what they require, they also are very reasonably priced.