I always liked how they got away with cash cosmetics being blatant copies and direct references of other anime/games/movies. There was stuff from star wars, FMA, the matrix, all sorts of things. Dressing up your character in that game was a ton of fun.
What private servers did you play on? I remember playing on one that had coders make neat plugins that added a lot of diversity and mini-events you could participate in. For example, trivia, hide and seek and even fashion contests where people had to follow a theme in an elimination per round show-off.
Geez, now I'm going to go listen to the main menu song again
Oh yeah I loved messing around with NX, I probably spent over $500 on it. And yeah, so many cosmetics are ripped from animes. Nowadays they do partnerships with them, I know there is like official Re:Zero, SAO, AOT stuff in game now. I know in JMS they did K-On! and FMA too.
I've played on tons. The most well known would probably be BankaiMS, OdinMS, or MapleRoyals.
GM events were pretty fun in pservers. I remember playing those fashion contests too, cute or boot is what I think it was called.
Maple music is great, you should listen to the track "Missing You". It almost makes me cry sometimes.