1. Right-click the image.
2. Click "Save As" and give it a name, as well.
3. Upload the image on ImageShack or some other image hoster.
4. Copy and paste the code for it into your signature.
A better way is to do this:
{IMG}IMAGEURLHERE{/IMG}
I find that it works better than pasting. Those fancy brackets should just be normal brackets.
Mumble's right. Here's my way, it's like Mumble's though.
there you go. Hope it helps a lot of you guys who need help posting their sigs.