You can delete an existing Photo Frame from your layout by clicking on it to select it, then hitting the Delete key.
If the frame contains a photo placeholder, deleting it removes the placeholder and the Photo Frame Properties, but leaves behind the geometric Shape on your page. You can change the size, color and border style and thickness of any shape and use it as an artistic object in your layout.
If the frame that contains an actual photo, then deleting it deletes the entire object (photo, frame, and shape).
Using the Clear command under the Edit menu removes the entire object.
Removing the Photo Frame Properties from a Frame that already contains a photo will remove the Frame, leaving behind the rectangular photo. This photo is then a static object in your Layout, and it will not behave as if in a Frame.