Yes, that’s a chair on top.
I’ve seen this van parked around my neighborhood for several months now. It’s always COMPLETELY AND UTTERLY PACKED WITH JUNK. The interesting thing is that the junk changes from time to time. Sometimes the cardboard in the window changes, sometimes the stuff on top changes, and due to “alternate side of the street parking” (Wikipedia article for those not familiar with the concept, and Jen Bekman has a nice little write-up of her experiences) it’s moved around, although judging from the junk in the driver’s seat, I have no idea how.
A quick inventory of what can be identified through the front window includes several CDs, a light bulb, a cable box remote, markers and pens, receipts, rolls or receipt paper that you might put in a calculator or cash register, third-class mail, sunglasses or swimming goggles, and a flashlight or a dildo (I’m not too familiar with either of those), plus a big piece of cardboard designed to keep the sun out, or, more likely, prying eyes away.
On top are several suitcases, a chair, a lamp, a wire storage thing that you might use in the bathroom or hang on the back of a closet door, a spray can of some kind, and a shopping cart. Most of it covered with a tarp.
The weird thing is that there is a Manhattan Mini Storage facility about four blocks away.