Here are some pics w/my moto for those of you who were curious as to how they would pair.
And DH has this to say:
Position the scarf so that the helmet is in the correct direction. Facing the scarf, the motorcycle on the left is a BMW Airhead set up for ice racing (see the spikes in the tires). The motorcycle on the right is a Moto-Guzzi that is set up as a Cafe Racer, you can tell this by the clip-on handlebars. It is distinctly a Guzzi because the cylinder heads are angled. The Motorcycle on the top is also a BMW Airhead, it is set up as a regular bike, but he doesn't know why they drew the mirrors hanging down. The motorcycle on the bottom is the same as above and set up as a Cafe Racer, you are viewing it from behind (see FSH in the review mirrors). The distinctive thing about BMW Airheads is that the cylinder heads stick straight out of the engine on each side. One of the speedometers appears to be brand new and one is used.
All of the motorcycles have control cables. On a typical motorcycle you have a clutch cable and a brake cable, these motorcycles are all connected via their control cables, the clutch cable of one motorcycle circles around to become the brake cable on the motorcycle next to it.
There are four saddle bags that can be used on either the horses or the bikes, and each saddlebag has a corresponding spark plug.
The motorcycle helmet in the middle has a reflective face-shield which is reflecting the bike directly below it.
I am sure he could go into more detail but it's late

I hope you found this helpful and interesting!