For what its worth, I just asked Amazon about it directly. Here is their reply:
Greetings from Amazon Seller Support,
I understand that you would like to know can you use google images to your listings to improve the quality of the images.
For your information, you can use images from other websites to your listings on Amazon but the image should not vary with the item which is on the detail page and also it should comply with the below requirements. So you can very well use images from the google to your listings but it should meet the Amazon image guidelines.
Your image must meet the following requirements:
-Images must accurately represent the product and show only the product that's for sale, with minimal or no propping. -MAIN images must have a pure white background (pure white blends in with the Amazon search and item detail pages - RGB values of 255, 255, 255). -MAIN images must show the actual product (not a graphic or illustration), and must not show excluded accessories, props that may confuse the customer, text that is not part of the product, or logos/watermarks/inset images. -The product must fill 85% or more of the image. -Images should be 1,000 pixels or larger in either height or width. This minimum size requirement enables zoom function on the website. Zoom has proven to enhance sales. The smallest your file can be is 500 pixels on the longest side. -Amazon accepts JPEG (.jpg), TIFF (.tif) or GIF (.gif) file formats. JPEG is preferred. -Product must not be on a mannequin. -Product must have good depth of field meaning the image is completely in focus. -Product must be clearly visible in the image (e.g., if on a model, s/he should not be sitting). -Image must not contain nudity.
Please refer to the below help page link, for information regarding Amazon image requirements: