There aren't enough posts using .GIF files. Markdown, the word processing language used on Steem allows for .gifs, or moving images. They really make the world a better place, so I remind you, it's totally possible on Steem. 

-As if we needed another reason as to why Steemit is superior to Facebook-

Make your own gifs here: https://imgflip.com/images-to-gif

Great source for uploading your .gifs: https://www.tumblr.com 

Keep it Steemy, folks :)