Neeta

Dear Friend, If u put your devotion and love for shiva even into a stone he will be there....So most important is your faith. Continue to Worship the one which you already started. Om Namaha Shivaya is the very powerful Mantra and if you chant mantra with faith and devotion god is already residing there...Apart from Om Namaha Shivaya if you want to chant other Mantra you can chant Mahamritunjaya mantra...or anyother mantra for Lorshiva...Remember Whatever you do with Faith and devotion will only give positive result...it doesnt matter which mantra......