It may seem like stating the obvious, but the structural installation must be addressed, too. It must be secured against all manouvering, gust, and emergency landing loads. This is an "item of mass" in the cabin which "may harm the occupants in the event of a crash". Simply bolting it to a plate would not be sufficient, because copiers often have loose parts (lids, document feeders, trays) that should also be secure. Having a procedure to stow loose items has come up on survey equipment projects where the scientists have keyboards and laptops sitting around. Somebody mentioned an EMI enclosure, which could also serve to keep the little pieces from flying. Wires also shouldn't be loose.
Will someone be sitting close to the fax/copier? Within a certain radius, you must consider headstrikes against sharp edges. Especially if your EMI enclosure is a bent-up sheet metal box.
Think carefully about 25.853... it doesn't seem like you have, otherwise you wouldn't have brushed it off so casually. I won't elaborate yet, because if I explain myself, everyone is going to jump. There are means of mitigating each of the issues, but you should brace yourself for a very strict interpretation of the FAR's from the ACO.
Just because others have had an "easy go" doesn't mean that you will.
Good luck!
Steven Fahey, CET