Indeed, there is nothing necessarily wrong with having some entirely blasé piece of colored canvas on one's wall if it improves the overal 'feel' of a room. To be sure, in many settings a piece of real artwork might be overly distracting and not really suitable.
Still, I do think there's a major "Emperor's New Clothes" movement afoot in the "art" community. Just as the shysters in that story pursuaded people that if they were intelligent they should have no trouble seeing the emperor's fine raiment, so too with today's "art" peddlers. While I'll readily admit that there are some forms of artwork which are subtle and require a certain amount of discernment to appreciate, much of today's modern "art" has no real artistic merit whatsoever.
BTW, I don't think anyone has yet linked directly to it, but I highly recommend www.artrenewal.org. Wonderful sight, with thousands of absolutely positively gorgeous artworks. I can't recommend that site enough.
Dear Miss Marple, if you haven't seen it yet, please check out www.artrenewal.org (described in supercat's reply no. 87 above). It might be of interest to your sister and your daughter.