Look at these images. As you know you can see different figures of people, animals and so on on the walls, stones etc and you can be healthy person at the same time )) And you can use it as art ideas. Just read about 'Pareidolia' if you want to know more.
Also if you're interested in these things you can read Austin Osman Spare. He says interesting things for artists: 'An »automatic« scribble of twisting and interlacing lines permits the germ of an idea in the subconscious mind to express, or at least suggest itself to the consciousness. From this mass of procreative shapes, full of fallacy, a feeble embryo of idea may be selected and trained by the artist to full growth and power. By these means, may the profoundest depths of memory be drawn upon and the springs of instinct tapped.'.
Thus writes Leonardo da Vinci: 'If you look at some old wall covered with dirt, or the odd appearance of some streaked stones, you may discover several things like landskips (sic), battles, clouds, uncommon attitude, draperies, etc. Out of this confused mass of objects the mind will be furnished with abundance of designs and subjects, perfectly new.'.
So it goes.