In Zencart, if you want to change the design of the button images, you’ll find them in the directory:
includes\templates\template_default\buttons\english\.
If you purchase or download a free zencart template on the internet, you will find them in the directory of your purchased template. Unlike other system, these images are not located under “images” directory. The reason for this setup is that it’s easier for multiple languages can be developed in the future. For example, if you want to add a set of button images in Japanese or Italian, you will just add another directory called “japanese” in parallel with the “english” directory.
In many old ZenCart versions, you’ll find button images in the image folder which can only support English. That’s why I recommend all ZenCart user to upgrade their shopping cart to the latest version or at least a higher version so that it can adapt to the new changes of the IT industry.