I'm in this situation right now. It was suggested to me to buy some round magnetic disks, recess them into the tiled panel substrate and a mating one in the framing (make sure you get the sides right, or they'll repell instead of attract! or you could screw a metal plate to the framing), then epoxy them in their holes. I plan to use some removable trim pieces on the ends. Don't know how well it will work! Another suggestion from a tile guy that I trust was to caulk the edges. This will act as a glue. WHen you need access, cut the caulk out, pull the panel, then put new caulk back in when you replace it.