It's possible that A: You're doing it wrong. B. The mods hate you just as much as Star Light.
To add images to your sig, go to your CP, and click on edit signature. There's a button that let's you add pics via url. In the visitor messages, it's between the "add hyperlink" button and "quote" button.
CLick on that, and paste the image url in there.
If you want to upload pics to your sig from your computer, first upload them to your album.