How to make all images on desktop and mobile the same

[VisibleZoo]

I have a simple Shopify Dawn-theme site full of 200+ digital downloads that I have created. I am going to watermark everything next, but I noticed that all of the images on my mobile are not the same - not the full # of images, and they all carry an"old" watermark that I want to erase.  Basically, I want what I have created on my desktop to always mirror on mobile. I do not code : ) Beta site: visiblezoo.com

[VisibleZoo]

Unfortunately, none of the links/replies below relate to my problem.