slightly old news, but custom avatars are back in the latest version of beat saber:

https://streamable.com/4jhk1c
https://streamable.com/t4q4v4

god I love dubstep. There's an example project for download in https://github.com/nicoco007/BeatSaberCustomAvatars/releases if you want to set up your own avatar, but I didn't get very far on that.