Is there luggage storage in Murano Italy near the vaparetto stop?
no
use the staffed luggage storage at the station (Ferrovia) before you cross the lagoon or leave your bags at your hotel.
btw - Murano has several (3 or 4 if memory is right without consulting the map) vaporetto stops - which do you mean?
Leave your luggage at the train station or at your hotel, as Nigel suggested; if at the train station, check hours of operation and allow time for a line when you retrieve it.