Sounds like a good overall theme, and I don't have a lot to add that other people haven't already mentioned.
My only big suggestion would be to have fun with, and play up the differences between the feywild, shadowfell, and paintings. All are equally dangerous, just in their own way.
The feywild is full of life and color to the point where it's almost overwhelming. The sun glittering off a cobweb wet with dew sparkles like diamonds, a babbling brook nearby seems to be making mystical music that entices you to just sit and listen forever. A huge danger is the shear beauty of the place entrancing mere mortals. And, of course, fey creatures may not technically be evil but they are wild.
The shadowfell is dark and dreary, with the color washed out of everything to the point where nearly everything is black and white. The sun is dim and distant, and it would be so easy to just sit and give in to the despair.
You can have just as much fun with the paintings. All the buildings, streets still look like they're made of paint. Perhaps some "creatures" are mere two-dimensional backgrounds that don't really impact anything, the 3-dimensional creatures are the ones you have to look out for. Because the walls are made of paint they may not be quite as solid as they seem.
The point is to make the feel different, not just from each other but also from the "real" world.