There is always something to do, even at home. Shop maintenance, remodel your showroom, come up with a better work flow plan and rearrange the shop for it. Come up with a marketing plan, make collateral materials and start sending it out or be ready to execute as soon as it opens up. Make templates for the cheap signs everyone complains about so they don't eat up time. Make some wrap designs to have ready. Re-letter your shop truck, redo your business sign, do a wall wrap, floor graphics for inside of your shop. Make a nice booklet or brochure to handout.
We have been making banners and sending them out as freebies. It keeps us in touch with our customers and they have a visual reminder if they need something. They're cheap and its better than sweeping a hole in the floor.