I do believe this comment is misleading in many ways. Most if not all properties available in the Design panel find their way into Relative Styling. If they don’t, rest assured there is a reason.
There are multiple reasons we have decided to not include a background image source option, yet, as we wanted to introduce it with dynamic possibilities, which requires a completely different perspective… But I can see by the different comments might not be a necessity for most users, so we’ll ship the static background image solution in the next couple of updates.