I have done it. In fact, I am just finishing up a quilt where I made a stencil of a music staff. I found a .jpg file that I wanted to use, enlarged it to the size I wanted, then printed it out. You can use card stock to print on, or you can use regular paper and transfer the design to something heavier. I ended up using a thin cardboard letter mailer that I had received in the mail and it worked great.
I used an Exacto knife to cut out the stencil lines, testing it to make sure the cutouts were wide enough to accommodate the marking pen I used. If you're using something like a pounce pad, the lines wouldn't need to be very thick at all.
Good luck. :)