Signature picture?

[CloudWatching]

I went to add Kate's name to my signature, and saw on the edit signature screen that I have a signature image selected that I uploaded a while ago that I'd forgotten about. But it doesnt display on my posts, is there a trick to making the picture appear in the signature when I post something?

I have had a look in the help forums but couldnt find anything specifically about pictures in the signature

Thanks