When God is present everywhere, why should we worship him in the temple images?
Certainly, God is present everywhere, but is he accessible to us everywhere? Water is present everywhere in the air as water vapor, but can we just hang out our tongue and access that water whenever we feel thirsty? No; we need to go to a tap. Similarly, though God is present everywhere; we need his accessible form as manifested in the temples.
The need for an accessible manifestation of God is indispensable. Even in the imaginary storyline of OMG, God appears before Kanjibhai in a materially visible form and protects him in miraculous ways. Only on seeing this form does he get converted. Thus, even a skeptic who rejects all material manifestations of God needs a material manifestation to develop his faith.
In real-life, unlike in OMG’s imaginary storyline, God doesn’t appear personally to each one of us – at least not till we are adequately purified. Then how can we access God? To help us, those saintly people who have seen him as he actually is in his transcendental form have described that form for us. Moreover, the scriptures tell us that we can and should depict God according to that description, for if we worship him devotedly he will accept our worship.
A movie scriptwriter may fictitiously make God speak that Deity worship is unnecessary, but that statement expresses the opinion of the scriptwriter, not the will of God. To know God’s will, we have to refer to the scriptures. And the scriptures strongly and repeatedly endorse Deity worship. For example, the Uddhava-Gita (Krishna’s instructions to Uddhava) comprises the largest philosophical section of the great devotional classic, the Srimad Bhagavatam, and it includes one full chapter (11.27) on Deity worship. Thus here the same Krishna in whose mouth OMG puts words condemning Deity worship speaks his actual will, enjoining Deity worship. Many other Puranas glorify Deity worship. And the Pancharatras are an entire library of books that systematically elucidate the principles and practices of Deity worship.