Hey @mariakarte
It looks like you wanna add a custom badge in your product pictures. As it’s not possible with CSS only and will require HTML and coding in your theme files so I suggest you to hire a Shopify developer who can help you out with that if you’re not familiar with coding. Feel free to let me know if you want me to help you out and I will be more than happy to help you out.
Best Regards,
Moeed