I keep seeing ads from Art.com that feature these four paintings: Four Trees, by Egon Schiele (1917); Pine Forest, by Gustav Klimt (1902); Dreaming Tree: Red, by Melissa Graves Brown, a contemporary artist; and Thatched Cottages at Cordeville, Auvers-Sur-Oise, by Van Gogh (1890). All very nice -- good living room wall material. I checked the site, and these are listed among their best sellers. Of major artists, only Van Gogh has more than one painting in their top 25, and he has five, all rural scenes from the Arles period. So if you want to sell lots of prints online, paint brightly colored country scenes in which trees figure prominently.