I made the money windmill, and I was tickled that you wanted to use it. That said, I don't think it worked well in a comic, and here's why:

Symbols and memes are everywhere on the internet, and they mainly work well because they pack a whole lot of information into an immediately recognizable and portable package. The symbol is already the punchline.

You can make comics which use these symbols, but they're bound to end up seeming weak, because they don't have any particular reason to exist. If we recognize the symbols and smile at them, we don't need a comic to remind us of it-- you can just show us the symbol and we'll smile. If you can show us a very original story, or character, or ironic situation, and incorporate a symbol into that, we'll fall out of our chairs. But if you rely on the symbols to carry the weight, it'll fall flat, even on those who understand what the symbol means.

When you're writing jokes for an in-group, you're bound to come up with a lot of crappy jokes for this reason.

My advice (FWIW) would be to not worry so much about making jokes about bitcoins, and focus on making jokes that people who like bitcoins would find funny. If you can make a few nods to the bitcoin community in the process, all the better-- but bitcoin itself isn't that funny.