Yes It should be an upsell product with a photo added to all order carts, no matter what.
It should be also optional, so a client decides ir add it to cart or not.
Gotcha, @lucia_B . In this case, there a few Upsell apps you can look into installing on your store. These all include the option to create an optional upsell prompt on the cart page:
The EasyGift app is the perfect solution for your requirement - it gives you the ability to automatically add a product or offer a range of products when a specific product or group of products are added to the cart.
Using EasyGift, you can set rules to automatically add or offer other items to your customers based on:
cart values
adding a product from a particular collections
adding a combination of products
rules for only specific customers using Magic links
EasyGift provides other helpful configurations:
link Shopify discounts with a rule
schedule a rule to run between specified time periods
Try EasyGift out on a 5-day free trial!
If you need help integrating it with your theme we can help with that too.