We are really sorry for the trouble, there content background may be dominanting your background image , so here is steps for that:
If you want to provide transparent content background color then please add this css on child theme style.css file
background-color: rgba(220, 220, 220, 0.82);
Note: 1> you can change background color as per your requirement.
2> It will be better if you place background option on tiled, because height of image may not be sufficient to cover whole page
3> Please use child theme style.css file to add css, so your changes will not lost on theme update.
We hope this clearify your doubt, if not then please let us know will be more than glad to assist you.