I was 'challenged' to make an ATC with nothing but wire. I finished two before my fingers gave out.
The first is a spiral inside a frame. Very colorful, heavy but sturdy. It's springy and bounces when you move it.
The second one is a tree. Mostly in gold and blue tones.
Both, of course, are pretty much 3-d. And the white is only background for photos (wire only, no card background.)
I know the challenge was a little non-traditional, but would they qualify as ATC's normally? They are the right size, but they really aren't cards in any way. More like just miniature wire sculptures.