We want Fritz Piece and Board on Lichess !

They are proprietary. So it won't happen, unless you would convince ChessBase to release them under permissive license somehow.

I think that there is a extension for that, you can check it out. (I last used it like 2 years ago.)
Edit: See this blog post for those extension
lichess.org/forum/lichess-feedback/sharing-custom-graphics

You can get close to other chess sites' default chess sets with these preferences.

For chess.com try the staunty piece set with the green board theme:



For chess24.com try the cardinal piece set with the wood4 board theme:



For play.chessbase.com try the meastro piece set with the maple board theme:



For freechess.club (FICS) try the merida piece set with the blue board theme:



For chesskid.com try the govenor piece set with the blue3 board theme:



And lichess.org is the cburnett piece set with the brown board theme: