How do I change the format of all pictures in a PowerPoint 2010 presentation?

If you want a macro-free solution, and reduced number of manual steps:

1. Select the picture that already has your desired formatting.

2. Press SHIFT+CTRL+C

3. Select each picture that you want to reformat, then press SHIFT+CTRL+V

After you've done these steps once, you can select the next picture and press F4.

NOTE: In a slide, you can SHIFT-CLICK to select many pictures. Then press SHIFT+CTRL+V to apply the formatting to all of them.

This little macro will do the job for you:

Sub AddPictureBorders()
' Before running this, apply the style you want to one picture
' then use the formatting paintbrush to pick up the formatting
' This will apply the formatting to each picture.
Dim oSh As Shape
Dim oSl As Slide

For Each oSl In ActivePresentation.Slides
    For Each oSh In oSl.Shapes
        With oSh
            ' ignoring linked pictures, OLE objects
            ' and such
            If .Type = msoPicture Then
                .Apply
            End If
        End With
    Next
Next

End Sub