Angels Bring
There are custom items. You go to sites where people make items and they allow you to download them for free use. Its not a cash item or similar.
Well, "officially" your wrong, there are no "custom items" unless she's talking about how you can kinda customize the stats on anything you make through the Item Maker Skill and adding stuff to make it better.
Unless your talking about editing the data, and making it where X thing looks new, like making a zhelm into a... let's say baseball cap?
Also in private servers, there's is a way to add in custom weapons(most just add in new stuff, like a .62 private server add in .75 stuff), though everyone needs the files that has them in or they dc if they see it.