To be fair, after playing around with this for a bit, I can sort of see why he did not wish to pay you. I know that seems like a heavy insult, but it's really not. He should have messaged you, and he definitely SHOULD have paid you for your effort and time. As a commission artist myself, I will always defend an artist's right to get paid for their work.
But... this is a very poorly made game. Despite the Stencyl problems you described, there is almost no variety in clothing whatsoever. Not even multiple colors of the same item. The body bases are all the same (even eye color) with only a different hair style. The skin tone doesn't change at all. Perhaps I missed it, but there is no option to change eye color either. Two dresses, a single pair of pants, two pairs of shoes, one (misaligned) pair of gloves... It does not look like you put any real effort into this at all. When I look at the effort you put into the eyes on the model, and then look at the complete lack of detail in all of the clothing.... It's really quite a disappointing difference.
Your commissioner should have paid you for your work, don't let him get away with that. But this dress up game is very lacking.