I've made removable floors for my pantry shelving and PVC cages, but just couldn't figure out a functional design for my Klubertanz cages that weren't clunky and ugly ... until now!
My problem was the frame - I wanted something black so it would match the cage wire, but paint wouldn't be safe. I also was stumped when it came to finding a way to attach the wire to the frame so it wouldn't sag with the weight of a wheel.
I found black powder-coated shelving standards (the long metal rails that you attach to the wall) at Ace Hardware. The wire floor is secured to the rails with strips of aluminum and stainless steel bolts/nuts. I used L-channels and L-brackets on the cage itself for tracks.
Here are some pics:
Completed cage without floor panel
Aluminum strips anchoring wire to frame
Floor in place