How to add a tiled background panel to UIElement tree (Editor)?

I am trying to create a tiled background panel based on a texture:

I want this texture to fill a panel by repeating itself:

In CSS this could be achieved with the property: "background-repeat: repeat;"

In the UI Builder there are background image fill mode options (section: Background in the Inspector) but achieving what I want does not appear to be possible that way. Can you think of a workaround that could be used to create the intended effect inside an editor window?

Thanks a lot.