New painting scheme...well...how about borrowing from fortnite? They are very popular so have some ideas that could help.
So we could have seasons that change every season in some way to develop lore and have speculation by those not in the arena, causing them to want to get involved and see what's going on. We could have maps that we often fight in (I know we have that but who looks at our maps now?) and have them change mysteriously in fun ways to keep combatants on their toes. Release special cosmetic items for winning tournaments, like your character can wear a cape we talked about in lore. Maybe they don't offer any real advantages besides lore and showing off or maybe they can do something cool, but of course these items would be limited from certain things such as tournaments if they are too OP unless we do have a tournament where all bets are off.
Focus on coolness over micromanaging details could work in the favor of this concept as newcomers tend to be leaning more towards. So it would be more casual, yes, but more fun for most. Those who favor strict attention to detail can still agree on such battles but the main focus would be on the fun stuff getting lots more people involved.
Main plot doesn't need to be fleshed out immediately but instead revealed over time. Rifts open up from different settings. Oddball assortment of characters pop into same world and decided on a tournament arc to get to know each other and settle differences. yay! So people don't need to feel the need to keep their character winning and surviving at all cost, the afterlife world also connects to a rift so we can come back with some plot whatever reasons why it doesn't work sometimes to add suspense but most common stuff it works to explain why heroes would slay each other in tournaments.
Also events that could be PvE, not just PvP, could be more common. Say we go on a quest for some secret treasure and everyone who participated in it gets a special coin they found in a chest. Each season participation can give you a badge you can wear as well.