Is there an option for applying a transparent background for an output element in a skin?

For example, in the above picture, this is a profile screen for the players in my game. The top box displays the player's name and a few images associated with various settings of that player. The larger bottom-right box displays a message the players can write, either a biography or advertising their various social media accounts or whatever.

Players can customize their background color and right now I just set the colors of these elements to match the color of the background when a player changes it.

I'd like to expand to allow for some background images on these screens, but the lack of transparency on these elements is making that a difficult process.
You're probably better off just doing the whole thing in a browser element, Windows has notoriously bad UI transparency support.