Instead of using the attachment option. Use the Insert Image button as it can still act like an attachment.
You don't have to upload the animation to a host, then copy+paste the url. You can upload the image straight from your computer. It acts like an attachment as well and there are less options to have to go through, instead of using the Manage Attachments Options.
EDIT: A better thing to do, is upload an animation to an image host, then use the