Homestuck - Ghost

Alright, I've been meaning to critique this one for awhile, so it's about time I got around to it. I'm just going to talk about a bunch of the tiny details, tell you what I think is good, what could be better, and what you could do to make some things better.

I'll start with background
The window is a little lopsided, but still looks alright, and outside the window looks really good. I like how it's not overly detailed, so it doesn't stand out too much. I also like the pictures on the wall. They look amazing (and I think it would be awesome if you made a similar sburb symbol as a separate drawing).
I like the way you colored the dresser, but it looks like wither you draw the dresser too far back, or the floor is uneven.

John-
His hair looks great and accurate. His skin is shaded well. The details on the clothes are good, and the creases and shadows are placed well. I like the details on and under the eyes, and his expression suits the character well.

Davve-
The fact that, while making him transparent, you were able to show so much detail on Dave like that really shows your skills as an artist. I'm sure you just put him on a layer above the rest and made him more opaque, but still. It looks great, and before I even read the title I could tell he was supposed to be a ghost.
I think the sunglasses look a little strange. I feel like they'd be curved around the head a little more, but that's just my opinion. I do, however, like the face shape. It really looks like /Dave/ in my opinion, and the opinion of many others. I don't know how to describe faces all that well, but this is pretty much the most popular headcanon for Dave.

I like the details you do on the ears, most people don't bother with that.
The overall pose of the the two characters is perfect. It really brings them to life; looks like John was in the middle of something and Dave came to visit him.