Difference between idol and vigraha. An article from a 1975 Back To Godhad by Jayadvaita dasa.
Are the Hare Krsna devotees idol worshipers? A senior member of the International Society for Krishna Consciousness resolves this question by explaining the authenticity of the Deity form of the Lord.
It’s natural for us to want to know what God looks like, just as it’s natural for a child who’s never seen his father to want to know what his father looks like. And just as such a child may imagine, “Maybe my father looks like this” or “Maybe he looks like that,” so we, too, speculate about what God must be like. The artist Michelangelo, for example, knowing God to be the original person, speculated that He must actually look old, with white hair and the features of an aged man. In this way, perhaps all of us have at one time or another formed at least some mental picture of God from whatever little we knew of Him.