Cool little piece. Sounds old -timey for sure. The first thing I would say (overall) is that its not loud enough, which is probably because of the fact that you were just winging it, but generally I think this is a pretty cool tune. I feel as if changing the theme is a neat idea, as I feel you did around 3 minutes in, on the other hand that change comes so abruptly that I kind of feel that it could be kind of hard for some audiences to digest. I think that there are a lot of neat ideas, esp. for something improvised on the spot.
That said, I feel as if the piece loses a bit of focus at around 7 minutes in. I'd really like to see where you take the themes once you have a chance to sit down, rework them over several versions. When you do, I'll let you know what I think of those as well.
Very cool stuff!!!! Thanks for sharing :)