I'm gonna move this thread to the Tutorials and FAQ section because it's better suited there.
That aside, how are you trying to paste the image in your sig? If you paste the exact code that NinJa included with the images, it should parse like this:
Just make sure the actual link to the image (
https://image.ibb.co/nJvNv6/Link2485_a.png) is wrapped in [IMG][/IMG] tags. This code should work for that particular image:
[img]https://image.ibb.co/nJvNv6/Link2485_a.png[/img]
If it still doesn't work, you can PM me your entire signature code wrapped in [plain][/plain] tags and I can try to help you out!