Today I thought I'd server up a few more that I've found since then.
One of the most interesting is this chalk drawing.
The idea here being that the light and shadow of the crater have been created by the chalk artist to make the hole in the ground look real.
The Escher stair case appears in many situations. Here's an overhead shot of an actual Escher-style staircase.
There are some interesting effects one can accomplish to create effects (like invisibility). While not "impossible objects" per se these effects are just as interesting. For example, with the right body paint one can virtually disappear in a public, open space.
These are images of Liu Bolin - a Chinese artist. Googling will turn up may more images like this.
Its not hard to imagine that others in the past have figured this out as well giving rise to various legends about people "disappearing" into the night and appearing out of nowhere. (As an aside about six years ago we had a very heavy rain - 5 or 6 inches in a few hours. A steep hill near our home was riddled with ground hog holes. The rain softened the earth to the point where the top three or so feet of earth in a forty by one hundred fifty (40' x 150') section slide down maybe six feet leaving a gap in the earth above the tear. It makes me think that stories of the earth opening up and "swallowing" someone are quite possible.)
When we hear about things, ghosts, spooks, demons, strange goings on in the night deliberate use of techniques like these is never really considered. Yet look how effect they really are.
These techniques do also appear in the real world without an artist to create them.
Take this photo for example.
A quick look will show that it appears that the woman's feet are mismatched with her torso - her left foot attached to her right leg, and vice versa. However, this is an actual, unretouched photograph.
What actually happening can be seen here:
You can see at the left (where her hand is photoshoped out) that everything is as it should be.
There is a physical touch equivalent to this visual illusion.
If you cross your fingers (see below where the middle finger crosses over the index finger) and take an object like the erase of a pencil and touch it to where the finger cross over you will "feel" two separate erasers.
Because your brain does not "realize" that your fingers are crossed it perceives that each separate finger is touching a separate object.
Finally, I leave you with this little gem...