I like to customize my desktop , so is there any compiz replacement for mir ?
EDIT : I mean , can we customize (Unity Next) and use compiz on it ?
Compiz is a compositing engine. It was designed to add compositing capabilities to window managers that run on top of X.
Mir has a compositing engine built in.
The two would be contradictory, so you cannot use Compiz on top of Mir.