The pins that many people have aren't actually managed in the signature field in your profile. You can acquire the pins with your 'points' (as seen under your avatar). To see the pin selection, click the yellow "Virtual Pin Shop" link above. As far as the character limit, every URL you include in your signature counts against the limit. To recover some of your space you can delete the tinkerbell pin since it already appears in your row of virtual pins. If you are still short on space you can try using something like tinyurl to make the URL shorter.
Let me know if you have any questions
