How can I upcycle a 3 level wall file organizer?

Here are some ideas: https://www.diyncrafts.com/24103/organization/25-brilliant-home-organization-ideas-magazine-racks-file-holders

You could make it into a wall organizer for mail and other things that tend to clutter up the counters.

use it for magazines, mail, even small towels...

If it is a commercial grade cabinet, as in thick steel,

take out the drawers turn it over on its side, spray paint a fun color,

put a bench cushion on it and dollar store bins in it.

Would be great for a shoe storage bench.

If the metal flexes when sat on, cut a piece of 1/2” plywood as a topper underneath the cushion. Or paint it “fun” in lieu of the cushion.

Not sure how big it is, but maybe you can put other things in it to organize - for example put spices in it and turn it into a spice rack.