I got a Mule Pro FXT last year. The first thing I did was use treated plywood to enclose the area under the front seat to create a storage area. In there I've put a cheap tool box from Harbor Freight, 12V air compressor, tow rope, toilet paper in a ziplock bag (sounds stupid but sometimes can be a life saver), and a first aid kit. I also added mounts to hang a machete and a hedge lopper behind the rear seat, I'm always running across something that needs cutting or trimming when driving the property
The most recent addition was a top to protect against rain and sun, and I decided I wanted interior lights.
For the lights I ordered a
rocker switch from Amazon that closely matched the existing switches. I also ordered a roll of waterproof
12V LED tape lights and
connectors . You can solder directly to the tape lights but these connectors are easier to use. These connectors in the link are actually splicers with connectors on each side, I cut the wire and use both ends. The adhesive on the back of these tape lights suck and will not hold. Here I put contact cement on the back to mount it, another option is good double sided tape. I positioned the tape lights so it will not shine into the eyes of those seated in the Mule, just shines down. This was a cheap addition, they put out a lot of light and I really like it. If one doesn't want to put a top on these could even be mounted under a roll bar.
I really like the versatility of these tape lights, cut to length and put in place. I've used them to replace the fluorescent innards of several trashed Thin-Lites in an RV, hidden lighting in a China Cabinet (with a transformer) and lighting in kitchen cabinets (again with a transformer).
On my to do list is a winch and a windshield.