Redesign on how Miiverse works and looks are on the way for the summer, EDIT: on July 29. We will also have an album to store 100 screenshot privately without the need to post them! And a Play Journal to record gameplay experiences.
Read about it @ https://miiverse.nintendo.net/special/redesign_announcement
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I think having their own screenshot album is quite nice, now there is no need to post them or upload to image hosters.
If only you had a button to take screenshots.