You could pay Photobucket their extortionate ransom, otherwise you will either have to edit your signature to take it off and leave it, or host your image somewhere else and use that. I'm sure someone will be along soon with a recommendation of a nice, user-friendly hosting site. I don't use them anymore, so can't help you there.
Use imgur instead: you don't need an account or need to pay to use it. Just upload from your computer, then right click and go "copy image address" and then, on HHO, to Ctrl+V in the "paste image address here" box.
Aaaand fairly sure this explanation makes no sense. But yeah, photobucket has kicked the bucket. ¯\_(ツ_/¯