hmm if it's returning the URIs then it's not the code... what file names are you passing in? maybe it doesn't like some special chars in there? Have you tried uploading just 1 image? The response text "PictureHeight" and PictureWidth" sizes have a wide variance.
Yea I've had all sorts of trouble with sandbox and these forums too :/
Honestly sometimes I do my "testing" on production
Also just to dot the i's and cross the T's make sure your pictures meet the following requirements.http://pages.ebay.com/sellerinformation/news/springupdate2013/picturerequirements.html Another test you can try as a control try uploading 1 of those images to a production listing (if possible) see if that works just to eliminate the sandbox "poopoo"ness scenario... ideally using the exact same code you are using now except pointing to production picture upload service
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