Mansions of Madness was one of those boardgames that sat around mostly completely painted for years before I finally sat down and finished it. The monsters were not as interesting to paint as I originally hoped. I varied the colors on the second wave of the better monsters, which I don't think will interfere with the gameplay that much. 
I did enjoy the investigators however, and found I was able to set a nice mood with lights and shadows on their bases. I worked this up with an almost watercolor consistency of painting, and it came out better then expected. 
The bigger monsters weren't too tough to paint, so much as time consuming. I got bored of painting these guys, but kept at it to finish the set out. 
So now I just need to get it to the table..