That should be worked but strange. Let me explain:
1. Copy the link below:
Code:
https://i.imgur.com/kVtBH7c.gif
2. Go to
Signature.
3. Click the "Image" icon (look at the picture below), paste the link and click "Insert" button.
4. Click "Save Changes" button.
(OPTIONNAL)
5. Copy another link below:
Code:
https://robertsspaceindustries.com/orgs/TEST
6. Select that animated signature (Ctrl+A), only signature should be showed in blue.
7. Click the "Link" icon, paste the link and click "Insert" button.
8. Click "Save Changes" button and you're done! ;)