Extra thought on Lost

I just got a Google ad telling me that I could own a copy of the mural from the hatch. This reminded me of that blacklight map that Locke found in the hatch. What was up with that? Was it relevant in any way? Is it ever coming back? And wasn't that guy in the hatch with Desmond the person who painted it? Wasn't he an Other? And if he was an Other then why was he going to leave on that sailboat? This goes back to what I was saying about Desmond and his story seeming way more important that most of the other despite how late he came into the show.