Google knows more about your images than you do. It scans images and builds a footprint, minor edits, resolution changes and renaming does not make the image unique therefor renaming the photos will do nothing for you.
While Google appreciates unqine images it also understands that images often get reused dozens, hundreds and even thousands. Reusing an image does not give your page a penalty, however... it would be fair to say that Google might have a algorithm that slightly increases page score with unqine images, additionally ranking better on Google image search too.
Google in your case would only give you a algorithm penalty if you had duplicate text content. Images only become duplicate when there's nothing else on the page and becomes similar to another site.
A good little tip if you don't know already to test Google's ability to detect duplicates is do a search on Google images for example 'sale' then click view image and download the image somewhere on your desktop. Then return to Google image search and drop and drag that image on the image search page, it then discover all duplications in different resolutions and minor alterations.