What's the biggest widget to be assembled from Shapeways parts? And the biggest single parts? Here's my entry-- a three piece hull for a model ship. It includes internal mounting features and stiffeners, much like you'd expect with an injection molded plastic model. Many large model ships are built on fiberglass hulls- usually nice on the outside, but with no internal features or datums, making the rest of the build difficult.
Look at the Max Bounding Box on the Material pages such as https://www.shapeways.com/materials/strong-and-flexible-plastic?li=nav Each printer (material) has different limits. In the case of WSF, you can go as large as 650×350×550mm with a single piece. With steel, you can go to 762×393×393mm There's no reason you can't assemble say 1000 separate pieces into a LARGE ship... assuming that you have the budget for it.
It can't be really big if it did not prompt shapeways to change their pricing Suspect biggest print by dimensions could still be dotsan's wireframe stag head sculpture of about 2-3 years ago, or one of the 3d printed fashion dresses. Time for a big things thread ? (I'm a miser, my biggest print still fits on a hand)
Maybe something like the dresses that are folded in the bed, and unfold when pulled out. So, you could tightly pack a chain, and when cleaned it could extend pretty far.