Hi Kefrem! Edit: Gauss' answer is better than mine. I had confused webp with webm. Derp. Webp does work, by all reports (I've never used it), but it takes a phenomenally long time to post-process them. An upload from start to finish can take hours, from what I have heard, and there's no clear message when their processing is finished. Also, how huge is huge? Maybe someone more experienced in animation uploading can be more informative, but I believe that there needs to be some wiggle room on the max file size to account for conversion on the Roll20 end. One of my hopes for Jumpgate eventually is that animated backgrounds will be better supported.