To Post a Picture in Your Signature...
Upload your picture to a web-hosting site. Photobucket works the best. Choose the direct link to the picture, you will know you have the direct link because it will end in .jpg (or other picture file). Another way to verify is to right click on the picture and go down to properties to see the URL.
Then go to www.tinyurl.com/
to make your URLs small. Use this code for your signature: <img src*="YOUR TINY URL HERE" width="180px" /> Take out the * and then you can change the size of the picture by adjusting the "180" up or down. (Make sure the URL is not bold.)