i think...your son is trying to illustrate how you guys went out on a hike/walk after the rain. he then sees the rainbow and was like eh? you then explained how rainbows form (i.e. the sun + water = reflection) hence the possible "H2O" letters he's trying to write out next to your face.

black unicorn poop - M please.

heyy I remember this!! I was there at the British Museum where this exact 3D painting was at and it was wayyyy cool!! =]

possibly a public chair...

or possibly part of the silk sorting machine.

It's part of a sewing machine (the end that turns.)