To make an image transparent in PowerPoint, you have to change the opacity of the image - and you can do it for the whole image or a part.

You can make a picture transparent in your PowerPoint slides so that you can add text over it or use it as a background.

After making the image a bit transparent, you’re ready to add the lines that create the collage effect. How to insert lines to create a collage effect in PowerPoint ...

When you add an image to PowerPoint, the program usually adds its own suggested alt text, which you can change. It's helpful to add alt text to your slides' images for anyone using a screen reader.