One should worship Me in My Deity forms by offering the most excellent paraphernalia. But a devotee completely freed from material desire may worship Me with whatever he is able to obtain, and may even worship Me within his heart with mental paraphernalia. (Lord Sri Krsna to Sri Uddhava, Srimad-bhagavatam 11.27.15) 

Even a liberated soul merged in the impersonal Brahman effulgence is attracted to the pastimes of Krsna. He thus installs a Deity and renders the Lord service. (Sankaracarya's commentary on the Nrsimha-tapani Upanisad)