My thoughts on the rider are that we need to minimize pieces - mainly to have a larger selection of pieces for the mount. Some might argue for leaving the design of the rider open, but I think we should "lock in" some variables to make the game fair. I think the mount is where we should allow for creativity. Just my opinion.
In the first rider I'm including here, I've just put together some quick concepts of what a rider might look like. The claws I rarely have a use for, so I thought using them for legs might save some other beams for the mount. I used the main body (with head/eyes) for the 2nd rider... (I'm also including a photo of the exploded 2nd rider for view of all the required pieces).
The 2nd rider design uses more of the dark gray pieces, but it's still fairly light weight and does resemble a rider (maybe not...).
These are just ideas... not final designs. I'll be curious to see what Brian and/or Matthias come up with...