You could double click the format painter (Home Tab) and click eech picture but that wouldn't set the size.
This code should do it:
Select the "master" picture and run
Sub makePixSame()
Dim osource As Shape
Dim osld As Slide
Dim oshp As Shape
Set osource = ActiveWindow.Selection.ShapeRange(1)
osource.PickUp
For Each osld In ActivePresentation.Slides
For Each oshp In osld.Shapes
If oshp.Type = msoPicture Then
oshp.Apply
oshp.Width = osource.Width
End If
If oshp.Type = msoPlaceholder Then
If oshp.PlaceholderFormat.ContainedType = msoPicture Then
oshp.Apply
oshp.Width = osource.Width
End If
End If
Next
Next
End Sub
How to use code