Are you using the correct image link from the site you've uploaded to? For example, I know Photobucket offers quite a few different options for links to your image.
For example:
This (the direct link) works perfectly without issues:
http://i60.photobucket.com/albums/h11/J ... 22979e.jpgThis is what Photobucket calls the Email & IM option. It will not work for Forum sigs:
http://s60.photobucket.com/user/Jellybe ... e.jpg.htmlThat Email & IM option is the sort of link people on here grab first when sharing their photos. Driving me nuts cause you've got to wait for the site to load which often takes longer than just the image itself xD