I found some brushes very similar to these a long time ago (which I loved) and I was looking through the shapes recently and suddenly realized that's what the person used to make them. So I've made some of my own!
These are really great and a decent size at between 700px and 850px. Feel free to use them how you want as long as:
You aren't making money off them
You don't claim them as your own (you don't have to give a link or necessarily put credit on your page, but if anyone asks you got to say you got them from me. Also linking to this page would be nice).
You aren't distributing them (you can link to here and point it out but don't load it on another site).
But other than that, you're good! Pretty painless, right? Have fun with them and be creative!