Being able to fill an entire slide with an image or video (perhaps with any aspect ratio mismatch-created gaps filled with black) would be neat.

This would be similar to how Deckset does slide-filling content and could be achieved by adding an attribute via Markdeep...

![](image.jpg full)

...and matching on this via CSS, something like this:

center img[full],
center video[full],
center iframe[full] {
    margin-top: -1rem;  /* counteract center top margin */
    margin-left: -2rem;  /* counteract side margin */
}
center img[full], ... {
    max-height: var(--slide-height);
    max-width: var(--slide-width);
}

I likely won't tackle this anytime soon, though.