I very much like the way you've used the colour yellow to bring out a warm feel to the whole piece, but the background kinda...i dunno..
Don't get me wrong, it looks like the whole thing is in another dimension and that idea comes out excellently, but still....
The framework, the glass and the texture also look fantastic.
One suggestion i'd like to make though, is to put a bit more stronger highlights to the thing. The hair, for instance, and the metal on the rail thing.
[Phew getting to be a long comment, but...]
One other thing that i feel strongly about and have learnt through experience is that one needs too have powerful strokes. I used to have really weak strokes and my teacher always chided me for it.
What i mean by that is, the strength of the shades weakens as distance increases: that is a part of perspective. In this piece, the background has near perfect shading, but the main character, the dude and lady do not because the strokes are merged too much. I hope u understand what im tryin to say.
Even so, the picture still looks good.