OK as one of the biker quilters I will try and see if I can help.
Type of rally you are going to is greatly dependent. Small local charity runs draw a much different crowd then a big national rally like Sturgis or Laconia. In my experience, at rallys us girls are the shoppers, the guys could care less unless it is some chrome gee gaw they can put on the bike itself or a biker accessory used in motorcycling. The girls are usually looking at the shiney things (jewelry).
However, quilty things can be of interest. I have made loads of T-shirt quilts out of HD dealer shirts. I made them for my local HOG chapter and we raffled them off. We usually had no trouble selling tickets at $5 a pop. $5 is easy to part with for a chance at a quilt, more not so much and a wall hanging, I just don't know if the market is there. That said, upon seeing my T-shirt quilt that was raffled off through the HOGS I have had 3 people actually pay me to make them one out of their T-shirts. They supplied the T's, I did everything else and they paid $400 for this service. So you just never know.
For the chrome on the bike wall hanging... Well it is an absolute pain in the butt to work with but silver lame may work. A few years ago I saw some very cool fabric at a quilt show that had silver metallic in it that looked great and probably a ton easier to work with than lame. But considering it is a wall hanging you may be able to find a silver acrylic paint you can mix with fabric medium to paint the chrome bits on. Depending on how much handwork you want to do.... sequins or shiney little tiny silver seed beads would also add just the right amount of shiney to represent chrome if you sewed them to a silvery gray fabric.