I personally thought this episode was great! I loved how Patrick's dim-witted personality was incorporated in his artworks (rocks with TONS of google eyes xD). I loved that scene with the art critic laughing at Squidward...it was very "loose-animated/expressive", just like the animation style from Ren & Stimpy it seemed. This episode closely relates to "The Artist unknown" in terms of art, but the level of humor definitely matches to that Season 3 episode imo.
My rating: 8/10