first off add the disguise plugin that lets people turn into objects (would be nice if anyone could use it or you just need like builder rank or higher) second off add a money system that people can give other people money and stuff (get money from play time like 1 hour = 1 money, also from other players and from trading tokens in)
You can disguise into pets by typing /pets. And what do you want to buy with the money? It's creative, so almost everything is for free, also for non-donators. ~Fault
people can trade custom banners, cool heads, hire people to build or anything really like pvp them, people can sell custom fireworks, coloured clothing and much more things
Like I said, you could get everything for free or just dupe it, there is no reason to add an economy to a creative server. ~Fault