It Has to Be Fun!
When a user creates a business card in a B2B system they are doing work. Its okay if the interface is utilitarian. You have succeeded if you can get the business card orders placed by your users and the business cards fulfilled.
The majority of turn-key web-to-print software is geared towards B2B. Look at Pixfizz,Pageflex Storefront, or XMPie uStore. None of these (or any other we have seen) are friendly for a B2C workflow. They only recently have started making any movement to really understand and adjust their cart systems to be friendly to Google for SEO. None of them have started working on the most important part of a B2C web-to-print system which is search.
When a consumer comes to your site to make a personalized item, whether a holiday card or story book, it needs to be fun. Think how much fun it is for a parent and child to go through creating a stuffed animal at Build-A-Bear Workshop. The value the customer is getting from Build-A-Bear is not just the bear. I would wager it is not even mostly the bear. It is mostly the experience of creating the bear.
Your consumer Web-to-print site must make sure to not waste the user’s time. It doesn’t mean you need to get them in and out and on their way. It means you need to make the time they spend in your web site fun. Your product is partly that fun and partly the physically shipped personalized item. Once you make it fun then you have one of the key components to a successful consumer web-to-print site.