How To Send Image To Back
In Google Slides
Open your Google Slides presentation and select the image you want to send to the back.
Right-click on the image to open the context menu.
Hover over "Order" in the menu.
Select "Send to back" to move the image behind all other elements.
If you only want to move it one layer back, select "Send backward" instead.
Adjust the position if needed by repeating the steps.