They do, but you have to click on them first and head to it's own page to see it in effect. It won't work on the page it's posted on. I'm not sure why it's like that though.
Hmm...Well I did find some sort of a wiki upgrade wiki
http://custom.wikia.com/wiki/Customize_Your_Wiki
Maybe we could upgrade it for Gifs..or something..I've seen Gifs work on pages before,like the Adventure Time wikia..
I've found a way to use GIFs. You have to take their URLs and paste them:
URL: (https://loveshistorical.files(REMOVE THIS).wordpress.com/2014/10/wtf-gif-tumblr-i2.gif)
Example: https://loveshistorical.files.wordpress.com/2014/10/wtf-gif-tumblr-i2.gif
Strange,it seems to only work with tumblr gifs.