In your position, I’d use custom post types and taxonomies. I could recommend the following:
With these you can implement a post-like group, for example products, and category-like taxonomy, for example brands.
Multi language support is a lot trickier, however, I have good experiences with:
For thumbnails, use post thumbnail function, it can be enabled in your theme init with:
add_theme_support( 'post-thumbnails' );
I hope it helped!