I am evaluating Ghost for some clients. Are there themes available or is it possible to customize Ghost to use for ecommerce sites and corporate websites?
yes, you can create anykind of corporate website in ghost. but ecommerce is not possible, because in ghost have no any payment method support, so if you want to create ecommerce website in ghost, you have to use third party payment method library. You can easily create affliate marketing website in ghost. If you need ghost theme developer, can contact with me.
You can integrate 3rd party ecommerce with ghost, there are some examples even on the forum if you search a bit. Easiest would probably be shopify light products.