Hi Philip,
To answer your questions as best I can...
"your back end seems strange" - I could not agree more...
"Does it come from Page Builder" - When you ask where it comes from, I am assuming your referring too where I was in the backend where I was trying to set the watermark in the screenshot? If so, I was in "Components->HikaShop - > Configuration - > Main - > Images If that is not what you meant, then I am not sure what you were asking.
"Anyway you can try to temporarily unpublished this plugin and see it that change something" - As I am not the host Admin, nor the original site designer, I will bring this up to my Developer and get his take on that. I don't know anything about doing that, and I am hands off when it comes to the backend server (ie Joomla, HikaShop, all extensions) so I will ask him to respond to your suggestion.
"And second, 300 x 300 pixels is by far very big for a watermark." The reason I choose 300x300 was because I was assuming the watermark would have been placed on the larger product image that the customer can click on to see what I will call the zoom, or full size image which is 800x360, and I wanted the watermark to completely cover the center of the image. I figured that HikaShop would have created a smaller version of the watermark for the "thumbnail" image on the product listing page. I have attached image where in lieu of a HikaShop generated watermark, I layered my own watermark on the images since I took the pics and wanted to deter others from stealing my handiwork. This way you can see why I chose the size of 300x300. I also attached the file I tried to use
for the watermark[/b]
"Other point which format do you use ? Jpg, png"
The watermark image I attempted to use was a PNG with a transparent background. Only the actual visual part of the watermark is in the image, the rest is transparent.
"Awaiting news from you." I hope I have answered your questions well enough.
Thank you!