Usually you set a background image that is repetitious – like your .png would have those multi-color balloons throughout the background image without the white space in it.

Then where your content was added you would add a background color / gradient to make the verbiage visible.

You can play with your div sizes, etc. on different devices to see what works best in that case. In this scenario there’s more control over padding a margin of the white space.

Hope that makes sense –
Cheers