How to rename images for multi language website?

Hello! I have a multi language website for photography with the following structure: …/bg. My question is how it’s best to rename the files for SEO. I want the bg images to be indexed in Bulgaria and the English ones in other European countries. How do I have to rename the images for the Cyrillic version - уебсайт.jpg or website_bg.jpg or just write images in English? Should I duplicate the images with names in different languages?

I have also bought a different .com and domain names for the English version which I currently don’t use. I thought I could change the language and website through the language icon but it will be a completely different website with the same images. Will this be considered a duplicate content although it’s in different language?