invisible background

I have some pictures on my screen and I want to put some variable numbers over them.
Space too limited to put the numbers under, or next to the pictures.

For the variable numbers I was thinking using labels.

How do I make the labels background "invisible" so it won't cover the picture, but only the text should be visible over the picture?

or is there something better than labels that can do the job?
or isn't possible at all?

thanks.

WM6.x? quite hard to do so, there are a few methods, free and paid