The below resources are some avatars that we really enjoy. They are great options to consider for your 3OV site.
VRoid Studio
VRoid is a program that allows you to create and customize 3D virtual avatars easily. These avatars are able to export in the VRM format, making them ideal for 3OV avatars and NPCs.
VRM Add-on for Blender
Crucial for building an avatar from scratch this Blender add-on has helpful tools for creating armatures and exporting VRM compatible avatars.
VIPE Heroes
Cross-platform and CC0, Vipe are a colorful and diverse catalog of VRM compatible avatars. Being CC0 these are awesome options for your site!
Phettaverse
His name is Phetta. He's a purple rat that lives in the Phettaverse and has lots of colorful friends. They're all VRM and compatible!
Boomboxheads
Boomboxheads are CC0 avatars that are generated by NFT mint. They are VRM and free to use in your websites.
Boom Tools
Open Source tool that can batch randomize layers in Unity using weighted randomization. It can export VRMs using uniVRM, as well as a posed GLB.