Upvote:1
The closest thing in the Bible that directly addresses the issue of the "form of God" is Deuteronomy chapter 4.
"Then the LORD spoke to you out of the midst of the fire; you heard the sound of words, but saw no form; there was only a voice" (Deut 4:12)
"Therefore take good heed to yourselves. Since you saw no form on the day that the LORD spoke to you at Horeb out of the midst of the fire, beware lest you act corruptly by making a graven image for yourselves, in the form of any figure, the likeness of male or female, the likeness of any beast that is on the earth, the likeness of any winged bird that flies in the air, the likeness of anything that creeps on the ground, the likeness of any fish that is in the water under the earth" (Deut 4:15-18).
Although someone could argue that the people didn't SEE a form of God but God may actually have one. That can be answered by the fact that God is a spirit (John 4:24). A "form" is a property of the physical world and not the spiritual world.
Upvote:2
This is a great question. 1 John 4:12, John 1:18, & 1 Timothy 6:16 all cross reference each other and all say that God (the Father in this case; I'll get to this later) has not been seen, and cannot be seen. It doesn't directly say formless, but we interpret it that way as something that can't be seen would logically lack form.
Now, you raised some good points about God walking in Eden, the Israelites seeing someone seated on a throne, etc., but that diverges from your question of God being formless into a discussion on the Trinity. The member/person of the Godhead (Father, Son, & Holy Spirit) that is referenced in the verses I referred to is God the Father, and He has never been, nor will ever be, seen. Again, a discussion on the Trinity is a whole new question for another time, and really should be a separate question, but I hope this is simple enough to reference for your question.
Awesome question by the way, IMHO.