Darryl Parsons is right. The easiest way to find out if you've stolen anyone's intellectual property is to publish it. When your phone starts ringing, let it go to voicemail.
hno:
Need a logo? Besides the copyright-free art books you can buy at any art supply store you can always grab a copy of the biggest city Yellow Pages you can find. Most all of the images in there are copyright free. It's an old trick. Obviously, don't grab Verizon's logo, etc.