Whatever includelets you place between the Background Begin and Background End will appear on top of the image/colour that you set up.

So what I would do is use the Custom Content includelet to create the text that you want to overlay on the background. You can choose to put this in a panel, or show it inline if you don't want the standard box around it.

You can then play around with the margin/padding settings on the includelet to add space above and below the text.

If you want ultimate control you could use the Raw HTML includelet instead of Custom Content - though then you're on your own with the appropriate HTML etc!

This is how we did the text over the main image on here: https://superhighways.org.uk

Thanks

Joe