On 6.2 also you should see a rendition only instead of the original image. something like 1280.1280 one or the one whose width is nearer to given width. I just figured out that as soon as you upload the image on 6.2 , for a moment while the image is being processed, it shows you the path of original because its still creating different renditions. Once the renditions are created, and if we reload the page again, it displays the 1280 rendition.
or while uploading image to 6.2, you must have disabled the update asset workflow launcher.
See the comparison in the getThumbnailUrl method in 6.2 and 6.4
/libs/dam/gui/coral/components/admin/contentrenderer/base/base.jsp
You need not do any changes or overlaying. And moreover why do you want to show the original image when the rendition is available ?
Also please mention if the images in your 6.2 instance had renditions or not?