For each language, you can create unique content with completely different images.
You can do it using Media Gallery (it exist for articles, products, collections, and pages content block).
To insert an image into the product description, follow the next steps:
- Go to "Products" => "Products List".
- Open necessary product.
- At the content editor menu find the "Insert Image" button.
- In the opened media uploader select exist image or upload new with "Upload" button at the bottom.
- Press the "Insert Image" button.
- Click the primary "Save" button.