Server I played before opening my own had about 6-8 wings, 5-6 headgears, 1 custom footgear, garment, shield and a few custom weapons (of course only the wings/headgears had special sprites). They didn't have custom pets monsters, they had a few quests from eA forum, so not totally unique, but different from gravity.
Server I'm currently admin we got lots, I like to customise stuff.
14 wings
23 headgears
11 custom pets with custom item for tames and food
Tonz of custom quest and events cuz I like to script XD
No custom monster yet, maybe in the future, one thing at the time lol
I don't think we're breaking any record, however, there must be servers with even more ^_^ Specially with xray, it's so easy and fun to add custom gears.