Lightbox Embeded Form: Ability to customize lightbox design

How to customize lightbox design? I don't mean the default lightbox properties such as lightbox frame style, width, height, title.

I mean changing of lightbox background color, border color, border thickness, "close" symbol changing, etc.

Currently, if you would like to further customize the light box layout you will need to inject some CSS code to the page where you're added the code, in the embed wizard you could only customize some properties. 

I will forward this to our second level as feature request, do note that we cannot provide an ETA or ensure this will be implemented, but we will let you know as soon as we receive any update about it.