One Image Background
Click the "gear" icon to change the layout of the One Image. This text will be removed on preview/publish.
You will see the result in preview/publish mode.
Edit you want to make transparent and replace background-color: @bgColor; by background:transparent; OR Background:rgba(255,255,255,0.5);
the last number are transparency value
Except in the blocks of my pack, which has a background transparency option