I don't know if this has been done before, but the whole point is to paint something that goes with a certain letter of the alphabet.
For A, you could paint an apple, an ambulance or an aardvark!
For B, you could paint a banana, a bus or a bench!
For C, you could paint a cookie, a car or a crying person!
And so on...
Basically, you paint anything that starts with the letter that is next.
Person 1: I paint an apple, for A.
Person 2: I paint a bed, for B.
Person 3: I paint a cookie, for C.
And so on.
I will start by painting an ambulance! And the next person will paint something starting with 'B'!
P.S. If somebody does the painting before you, don't panic, either paint something else and edit your post, or, make a note in your post saying it was a duplicate.