It's a good first brush! It is reeeally dark though. Maybe try and lighten it up a bit and feather the edges? So people can use it like a stamp tool. With the hard edges you have it really makes it hard to use in any kind of pattern. Thanks for makin it though and I hope this helps.
Yes, you should use a really bright colour on the back if you want to use this brush. And yes, it has "hard" edges, maybe I'll do that later on. But because the brush is really big, you can easily use them as a background for signatures, and you wont have to worry about the edges then.