Regarding your questions about the difference between the picture of Krsna and the Deity, Krsna is equally there in both these forms. Krsna is so kind that he agrees to appear, for the benefit of the conditioned soul, in eight different kinds of forms. Such form is called arca or the form of the Lord manifested through material agency as metal, earth, wood, painting, stone, jewel, drawing, and mind. The arca is accepted as incarnation of God, and is worshiped by regulations. Generally the installed Deities are so worshiped and the regulative principles should be strictly followed in regard to Them.
Letter to Linda, 19 February, 1970