I have just looked at Setting in the Win8 Metro App and cannot see why you are getting both small and large photos. Have you looked at your Photo App settings to see which sources are being supplied to the App? Mine has only Pictures Library ticked but there is also an option to tick SkyDrive, Flickr and Facebook - perhaps they are the source of the thumbnails.
Spell checker for Photos, what relevance has this? For labeling perhaps?
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