Audio normalization could be implemented in two levels:
1) provide a volume slider in each video entry, so that you can differentiate volume per Media
2) normalize volume for all Media
Both ways are right now unknown, and we have not had enough testing to say if any of the two is feasible. As soon as we do, we will update you here.
Turns out that setting a solid color background or setting an image as a background is easy. We will provide this option soon.