Most people add eagle eye lights, Radios, car horns, basically any 12v accessory you can think of will work just fine one these.
One of the best first mods to do is to trash the stock charger and get a decent aftermarket one. Stock chargers kill batteries due to the low charging voltage, long charging times, and no float capability. For 20-30 bucks you can get a decent one that will Charge faster, Charge smarter, and float charge when full.
Next up is to make it easier to charge your battery. I personally take a 4 flat connector from walmart and run it out the back of the ride on. Then I can charge the battery without removing it.
https://www.walmart.com/ip/Hopkins-Towing-Trailer-Connector-Set-48-in-Vehicle-Side-4-Flat-48205/16782546?fulfillmentIntent=In-store
Just splice it into the stock wiring or cut the stock connectors off and use spade connectors.
The stock battery is ok, but run time is low. Upgrade to a 12v 12ah for about an hour and a half run time. amazon.com/ML12-12-Battery-Terminal-Mighty-Product/dp/B00K53FG5Q/ref=sr_1_1?dchild=1&keywords=12v+12ah&qid=1634649045&sr=8-1