Is the background from the original stock? Doesn't make sense to keep it - get rid of it and make your own, even if it's a simple solid color or gradient.

Not bad for a first. Some shapes still look shaky, and although better than before, still needs work on the pen tool technique.

Definitely needs more emphasized highlights and shadows like Garis said - it's too dull overall. It looks like you used partial transparency for shading, which I wouldn't recommend. It doesn't give you enough control, and if you're using blacks/whites for shadows and highlights, then you get stuck with one hue, which makes it look bland and unrealistic. You generally want to use full opacity for each shape and pick your own colors.

Good job for your first - keep practicing.