Add ability to add an image background

[mscx-rails]

We use Gitbook for our Help Center, as a way to never have to go back to Zendesk (eventually).

However, the formatting ability on the home pages is quite boring, and don't allow for a lot of customization for brand elements outside of logos. A simple loadable .svg file would be great!

[addisonschultz]

Hi @mscx-rails, definitely something we’re exploring. Stay tuned!