An image that is an object of worship is an idol. Examples could include crosses, pictures of Mary, etc People will say that these images are aids in worshipping God. But the real question is, what does God think about use of images in worshipping him?. His Word the Bible gives his feelings or reactions to this.

Exodus 20:4,5a says "You must not make for yourself a carved image or a representation like anything that is in the heavens above or on the earth beneath or in the waters under the earth. You must not bow down to them or be enticed to serve them".

You will notice that the prohibition is against making of images and worshipping them. The Israelites made a calf image and says the calf image represent Jehovah God, but God was angry with them for making a representation of him.(Exodus 32:4-7)

So from just this two verses, it is clear, that use of images like cross, pictures of Mary and other things that people say are aids in worshipping God is not right and Jehovah God himself does not want it.

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The same God instructed Moses in Num 21:8-9, “ Make a snake and put it up on a pole; anyone who is bitten can look at it and live."
So Moses made a bronze snake and put it up on a pole. Then when anyone was bitten by a snake and looked at the bronze snake, he lived.

And Jesus made reference to the image of the bronze serpent in John 3:14-15 “So Jesus tells Nicodemus “As Moses lifted up the serpent in the wilderness, even so must the Son of Man be lifted up; so that whoever believes will in Him have eternal life.”

The images are not to be worshipped and bowed to and proclaimed to be God, but if looking at them reminds you of what God has done and is doing and will do and reminds you of his Word, and increases your love for him and your Neighbor, then you are good to go. Just as looking at the pictures of a loved one reminds you of them, what they do and say (sometimes we smile while doing this) and increases our love for them.

Example: Looking at a Crucifix that reminds you of the sacrifice Christ went through because of your sins at a point when you are tempted to sin again, chances are that you will think twice at that point and perhaps desist from going on with the sin.✅��