According to some of the replies in this discussion, even "artist trying to paint from memory" is guilty of infringement, as long as the subject matter can be linked in any way to someone's "IP". Im not legally trained to evaluate these claims, but some of them seem outlandish!

> According to some of the replies in this discussion, even "artist trying to paint from memory" is guilty of infringement

Yes, making a copy or derivative work of something under copyright from memory is infringement, unless it falls under an exception in copyright law such as fair use (which does not categorically apply to everything with "memory" as an intermediary between the original work and the copy/derivative, otherwise, copyright law would never have had any effect other than on mechanical duplication.)

Painting and selling a painting or otherwise substituting that painting for an original work that deprives the original creator is theft, plain and simple. Not selling it, there's room for discussion and more considered legal review.