Zakeke allows you to offer product variants.
Zakeke gets the variants from your store and this is the only way to set the variants within Zakeke. It means that you need first to set the variants of your product in your store and, once done, you'll be able to see them at the first step of the step-by-step wizard to create your customizable product.
Warning: if you use WooCommerce or BigCommerce and despite having set the variants of your product on your store, you are not yet able to see them on Zakeke, read here.
PRO TIP: you can allow your customers to order more than one variants with the same design at once.