I don't see how you could be anything but thrilled with what you've created there. I'm in complete awe of this. But, if you insist on being disappointed with it, finish it up and send it to me so that you won't be haunted by it for all eternity.
Seriously, you may just be too close to it (and at that scale, how could you not be?). What you may need to do is take a little time off from it so that you can approach it with a clear head.
Not only can't I wait to see this when you've finished it, but I am eagerly anticipating the large version, as well.