You can actually print anything you want on spi's or other sails with large scale printing machines that are used to print advertising banners, should be cheaper then hand painting. If you were in Romania I could have helped you out.
Ask somebody that works in an architectural bureau or advertising firm. There are some limits depending the print machine and type of media feed mechanism. You can also print the patterns on adhesive paper (large scale) and make templates on the spi and then paint yourself (cheapest). If you are really interested send me drawings and I'll send back templates (.pdf -can be printed in any print shop).
Template method id easier and cheapest if you're near a print shop. If you want to get it even fancier you can make the templates on a cut&plot machine, that way you don't have to manually cut the areas to be painted.

You can also cut the drawing out of a special film that can be applied to the spi by heat transfer. The film is very thin and can be applied to very thin materials like the nylon material of an umbrella. The film comes in various colors, and not too expensive (16Euros per sqm).
Siser is one of the manufacturers of this kind of films. The cutting can be done either manualy or on a cut&plot machine.