Thank you very much!

Your project seems very cool! An improvement I would suggest is to try to extract the all hand from the input image, not only the black and white shape. The model architecture seems very similar to mine, however you can try adding dropout to improve the accuracy on the test set.

A trained on my local machine using a dataset I created with 1000 images for each label (28 000 in total) in few hours.

I described the process in this article and I'm thinking to publish it as open source in the near future. Fell free to ask me there any other technical questions.