60 frames logo
My god I just noticed it now how much it looks like a spinner!
You kids and your spinners....
I'm not sure what it's meant to look like so I don't know whether it's slowed for me, but some browsers have a minimum frame delay, and ~.017s (60fps) might be below your browser's minimum.
Your preview image looks auto-scaled down. Previews are subject to the same rules as the detail file, so they should be hand-crafted pixel art. You could clean up the scaled down version or use a crop of the full version. If you want this piece to show up on the front page, I recommend using a non-animated preview. Animation makes for a larger file size, but only preview files up to 10kb in size are displayed on the front page.
Why it is not 60fps? I set it to 60 but looks like 40-50 to me