You could adjust the Master layouts, and then reapply the appropriate layout to slides as needed. However, if objects on the slide aren't in master placeholders (that is, if they were inserted directly on a slide), you'll have to move them manually.
For manual repositioning, I suggest you pay attention to the X and Y numbers in the Size and Position area of the FORMAT ribbon:
For example, if you determine what the new position should be for inserted photos, you can select a photo and then enter the numbers to move it into that exact position.
It might also help to turn on the Guides, and adjust those so you can quickly move objects into place.
Good luck!
