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. On the other hand one isn't allowed to create an image on his own and give it form and then call it to be something godlike (divine)
Looking at these prohibitions (see for example Exodus 20:1-4, Deuteronomy 4:15-19, Deuteronomy 5:6-9 etc.) I noticed the emphasis on making such images physical. But what about the 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. Is there any verse in the Tenach which explicitly shows images of G-d in our heads (thoughts) are prohibited?
P.s. Another question I have regards this topic is that the presence of 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?