Go on Google and find the picture you want. Left click the picture so it opens it in larger display. Right click the picture and click Open In New Tab then copy paste THAT link.
For example, try copy-pasting this link into your signature through the little picture button on the top: http://todaymade.com/blog/wp-content/uploads/2013/03/troll-face.png
dude don't click it, I'll try to post it without it linking tho: http://todaymade.com/blog/wp-content/uploads/2013/03/troll-face.png
You are putting the URL to the page that the image/GIF is on which doesn't work. You need to put the direct link to the image/URL for it to show up, and you can do that by right-clicking on an image, selecting "open image in new tab," and copy/pasting that link into your signature. Here are the direct URLs for the ones in your signature: http://i.imgur.com/Q1kErRz.jpg http://fc07.deviantart.net/fs70/f/2014/319/8/5/new_freddy_by_crueldude100-d86gyv3.gif