Any ideas on how to cover a switchplate with fabric or paper?

I would try spray starch or fabric glue , on the plate and then put the fabric on there cut a cross in the Middle where the light switches and folded under.

Or you could just spray painted.

Switch plates are not expensive, replace with new ones the cost will be the same by the time you purchase the material to cover them

Modgepodge? They make different formulations now including one for fabric.

https://plaidonline.com/products/mod-podge-fabric-8-oz

Just glue the paper or fabric on the plate, folding some excess to the back. When it's dry, cut an X in the switch hole, fold the fabric/paper back and glue it in place. Poke holes with an awl where the screws go.

I used mod podge; remove plate from wall, spread with m/p lay face down on fabric or paper. When completely dry, use an Exacto knife to cut out the holes and trim around the edges (or fold edges over and secure in back of plate). Was really easy and looks great.

I bought mod podge and x-acto knife today and will give this a try! Appreciate the helpful feedback!!

Mogpog or diluted elmers glue