Sounds like split timelines here. It's easy to grasp. One line has Van Gogh originally coming up with an idea, while the other branch has him get inspiration from his "future self". However, when the inspired Van Gogh proceeds to make his version of the painting, his is most likely going to be at least the slightest bit different, and history will play out differently than it originally did. It wouldn't work as cleanly as it might have in Doctor Who.

@Super Nes: Yes, time travel IS fun.