Mounting a PCB with velcro
The Velcro is probably no worse than any other plastic (nylon) that is close to your circuit, as far as ESD is concerned. It may be a problem if you frequently rip the Velcro off, as you may cause the friction to generate a charge.

But a big problem with Velcro is that it does not last very long. The self-adhesive side will stick OK to begin with, but will dry out and let go in a comparatively short time. I've seen this happen on a regular basis with electronic modules fixed to housings with Velcro. They all came back with the modules dropped off but the Velcro-to-Velcro interface intact. The Velcro had just come unglued from the inside of the housing.