Single background image on page with multiple rows

I want to create a page with a single image as the background for the entire page. I am using Visual Composer in the Highend Theme.

My problem is that i need the page to include multiple rows with different numbers of columns in each row. I want to overlay all these row over the same background image.

I know how to create the image background behind a single row. How do i create the single image for all of the rows?

Alternatively, I have tried using a single row set to one column and then adding Visual Composer shortcode to create the columns. Then my problem becomes that the columns are not vertically aligned. The second column starts a line below the first.

Thank you all in advance.