Using alf's example.
1) go to tinypic.com.
2) upload image by clicking browse, then upload.
3) 3 fields are given to you, copy the one in the middle where it says [ IMG ].
4) After copying that line, go and edit your signature here on golfmkv.
5) Paste what you copied just now into your signature.
6) Enjoy the wonderful world of an image signature.