Over and over again we read about the prohibition of idolatry in the Tenach. In the first place G-d commands us not to make any physical image of Him, or anything that represents Him, but what about images in our thoughts/mind? We all have an image about G-d (of whom He is and what He does or can do, i.e. His attributes or characteristics), but I don’t assume one is allowed to have an image of G-d. Also, HaShem is often pictured in the Tenach as a cloud or to dwell in a cloud (1 Kings 8:10-11, Exodus 19, 40:34-38 and other verses). I’m quite a visual thinker, so is it wrong to picture these kind of images in my head. Is it wrong in this case to imagine G-d to dwell in a cloud. To sum things up: When does thinking about G-d or picturing G-d in the mind becomes idolatry?
Being that we can’t understand the essence of God Himself, we should rather be preoccupied with His attributes (merciful, forgiving, patient, etc. see Shmot 34, 6-7), which we not only can, but we’re even meant to emulate. The parables like “cloud”, or God’s “strong arm” are meant exclusively for poetic, not literal, use. If you accidentally find yourself imagining God like an old man or the like, simply dismiss it like any other subconscious childhood picture which we mistakenly still "carry" with us, despite its absurdity.