Your comments

I was responding to Techwolf's comment, where he seemed most concerned about lawsuits.

People can certainly die from seizures, which in the case of photosensitive epilepsy can be triggered by flashing lights or certain shapes. But is it a website's responsibility to not display content that may harm a tiny percentage of users? Or should the user be managing their illness responsibly by being careful and not putting themselves in situations that may harm them?

The real threat isn't found in animated user icons, anyway. The true killers can strike on any website, any time. No matter where you browse, you might be only one click away from death...

> Loading a page with 20 1Meg gifs
It's been proposed that instead of gifs, animations will use HTML5 video technology to greatly reduce the necessary filesize. According to sites like gfycat, these technologies use 10 times less data than the equivalent GIF animation. The avatar upload form might accept animated GIF as an input format, but would transform it to a smaller format before use.

> on a mobile device
I don't feel that animated avatars would be suitable for a mobile experience, I'd expect them to be off by default or even unavailable on mobile.

> Lawsuits due to you know a user will upload a animation that will trigger an eplitic attack.
I refer you to 47 U.S.C. § 230. Section 230(c)(1) provides immunity from liability for providers and users of an "interactive computer service" who publish information provided by others. This is known as a "safe harbor" provision.

Require a static upload in addation to animated. This is so one can either turn it on or off.

I'd expect that settings would be implemented to allow users to disable the display of animated avatars. However, instead of a separate static upload, I think the first frame should simply be displayed as a static image. This is overall less complicated and easier to understand than having two separate uploads that might be wildly different.

> This will prevent one from creating several accounts and uploading 2Meg animation and commenting on artwork with all accounts, creating a 20Meg download for all users that veiw the artwork.
Then that's spam and would be dealt with as such.

> opt-IN, this will prevent lawsuits and complaints
I support opt-in. As for lawsuits, see above. (Seriously though? Filing a lawsuit because visiting a site used your download quota? Anyone doing that would be laughed out of the courtroom, if they could find a lawyer who didn't laugh them out of the lawyer's office.)

WebM via the HTML5 <video> tag seems like the ideal technology to use behind-the-scenes to deliver animated icons. In practice you'd provide MPEG-4/H.264 fallback, since WebM is only fully supported on about 65% of all browsers.

Ideally, you'd use something like the below code:

<video autoplay loop muted poster="profile.png">
  <source src="profile.webm" type="video/webm">
  <source src="profile.mp4" type="video/mp4">
  <img src="profile.png" alt="">

Note that the <img> tag will only be rendered if the browser does not support the <video> tag.

I noticed you mentioned GIFV, however it's worth mentioning that this is not an actual file format; rather, it is Imgur's way of delivering HTML5 video (webm/mp4) in a format that can be viewed and linked to as conveniently as an animated GIF. Embedding a gifv is unfortunately not as simple as sticking it in an <img> tag.