Copy space, right or left ?

Hello,

I would also say that it depends on the image, what the image may say, or what the image could be used for.

It depends on how it will be used.

Most left-to-right readers will see text on the left side first.  Right-to-left readers will see the right side first.

And then there are social media content creators who put text on top & bottom of images. 

Often, the subject would determine the best placement for copy space. With a portrait for example (human or animal), if the subject is looking toward the left, that is where I'd put the copy space. If looking toward the right, I'd put the copy space on the right. Otherwise, I don't think there's any hard and fast rule for where it should go, though I myself generally lean toward the left. Or the right. No, the left. Wait...

Again, the subject more often than not will dictate. And, in many cases, the buyer can simply reverse the image as needed. 

Probably doesn't matter, because designers can easily flip the image horizontally and use it either way.