For a one-week work, while trying to also learn new hardware and software, you've done a bang-up job! The watercolor 'look' is unique, and suits the style perfectly - the 'sloppiness' gives it a very real, 'non-digital' feel. I don't honestly think it would be better with more detail or polish.
Just out of curiosity, the backgrounds look like you may have modeled them. Is this the case? I know there are several 2D comic artists now working with SketchUp to create quick-but-accurate interiors and exteriors, that they then integrate as backgrounds with their hand-drawn characters ('hand-drawn' by way of a tablet, usually).