There sould be a way to manage the uploadet screenshots. Give them the order you want to display them.
http://i.imgur.com/3hOK8tn.png
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Also, it would be a nice feature if you could upload Thumbnails for the Addon Gallery to represent your Addon.
The Thumbnails should have a fixed size to prevent a shift like this one:
http://i.imgur.com/a8KcwUJ.png
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If users upload Thumbnails in the wrong aspect ratio you could fix this with a blurred background script like in this example:
http://i.imgur.com/pnVzBQc.png
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All the best
Nick