Change image opacity

I’m using overlap to cover an image over some content…
Was wondering if I could make that image opacity less than 100%?

No, not in any settings in Foundry or stacks that I am aware of. But, a simple google search I found this. https://www.w3schools.com/css/css_image_transparency.asp

You could try and target the image with css. Each stack has a CSS classes entry box under HTML of the stacks property.