https://www.myknowledgemap.com/ offers a free online tool for badge creation at https://www.openbadges.me/. Log in with your email address and you can begin to build OBI-compliant badges with their selectors for shapes, type, icons and colors. Like these:
If you get an account at Mozillians, you can create badges there as well.
Hi, just to let you know we have updated http://www.openbadges.me so you can create even better badges, we have an all new badge designer and you can now also issue badges as well.