This is not a picture of God, though it is titled White Tara. White Tara is an idea sublimated in art.

Michael Angelo does not know what God looks like.

Buddha did not really fight with an army of demons.

So, Why would Gods appear to sadhu when we meditate? Perhaps because this mind of ours must put into image whatever it is thinking about, before thought puts it into words. Perhaps some concepts can only be visualized. The mind must have an image to grasp onto before it is silenced. As any sadhu will tell you, his mind is always preoccupied with God. At the same time, a sadhu will also tell you, God is not this image or that. But they will use those same images to tell a story, to make a point.

The Hebrews actually have a rule against making God into an image, lest we become confused.