"Novel art" in exactly the style of Monet, is not entirely novel. I think it would be reasonable to allow Monet to have sole right to produce his style for 7 years or so, and then it enter the public domain. That rewards coming up with a new artistic style, which I feel is at least as valuable to reward as coming up with a new piece of artwork in an established style.
Again, my art history is weak, but when Picasso came up with his first cubist work, the cubism part of that work seems as valuable, and worthy of reward, as the actual instance of cubism that the work embodies?
There's a generally derivative style that follows the spirit of the age, and then there's a clearly copied style from a specific maker/creator/artist. It seems poor to protect the individual instance of an inspiring new style, but then not reward the creator of that style, not even with an acknowledgement.
FWIW, I'm not sold on either side of the argument. To me that's not how online discussion works. Also, I absolutely would not want copyright terms of the length we have to protect anything like this (nor anything really, they're obscenely long).
I would not of course want to inhibit the natural progression of styles, Monet's landscapes bore some similarity to JMW Turner, and a Chinese style called Lingnan, but this is a different thing to taking Monet's pallette used for water lilies, then painting a similar subject in the exact same style. If you do that immediately after Monet first presented his style for water lilies then I'd at minimum want you to say 'in the style of Monet' as a subtitle, and preferably have to pay him a little of your profit for the first few years.
Thanks for your interesting, thoughtful responses.