Full-Screen Letterbox colour change?

Hi. I'm doing a web app and really appreciate the full-screen letterbox ability, introduced in r91, but would like the ability to change the colour, or even do a rudimentary customization of the background--adding in some form of texture, or tiledBackground instead of pure black.

How difficult would this be to add?

Also, I'm wondering on the wait-time for per-layout-loading.

Thanks guys.

You can do it trivially in CSS. Edit the exported index.html and change the background-color or add a background-image.

Would it be possible to add elements like buttons to the letterbox area using the anchor properties?