Keynote master template with images

Is there a way that I can arrange images in a template, lock their location/movability, but still have the image content itself editable when editing individual slides?

The definition of locking an object in Keynote is: "prevent moving, modifying or deleting"

Therefore what you want to do is not possible.

I work with many objects on different layers and need pixel accurate positioning, I lock the objects using

command L, when I need to edit I unlock the object using alt command L, then lock the object again when I'm finished.