AN IMPORTANT UPDATE: As of April, 2013, Shapeways no longer offers this high polygon workaround. If your model has over a million polygons, use this handy tutorial to reduce them so you can upload your model in the normal way. Thank you for your understanding!
Ok Zbrush users, organic algorithm artists and character modelers, Shapeways have developed a workaround so that your models can now exceed the 1,000,000 polygon limit currently in place.
It is not elegant, and takes some negotiating, but if we get enough demand we will try and automate the process to make it easier for everyone. Let us know what you think, is this something you would like to see as standard?