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Been doing this for along time.. either I missed it or they forgot to mention, before tapping done, you can tap through each photo and adjust its size
 
been using this feature for a while and it's great. Now I need a feature to remove time and date and everything else from the lock screen.
 
Hey Siri one figured out a way to make it show more than just a few pictures? I have an album of about 100 old-school Mac wallpapers from the jaguar and panther days but it only shows like the previous post above said about 16 photos.
 
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