Custom Website Developed Similar to Casetagram.com

Our business makes custom phone & tablet cases, so we'll need the ability for customers to upload their artwork/pictures into a maximum of 15 different templates that we have for the cases (think top/bottom layout so they can have 2 family photos on one case, heart shaped template, etc). We would need them to be able to adjust their pictures, ideally add background color and text, and most importantly they need to be able to see a virtual mockup on their screen of their case as changes occur in real-time. It's very important that they preview what their case looks like as it's being created. We want a website as similar to [login to view URL] as possible & it needs to be compatible with mobile devices as well, so if my assumption is correct, it would need to be an HTML5 site and I've been told that a good possible backend would be Loaded Commerce (OScommerce). On the back end, we'd naturally need the ability to download the pre-sized art file (that'll need to fit our printing template) and keep it synced up with the order/customer profile so we can provide automated order updates. Here are some other features that are important for our site: - Our customers need to be able to see a real-time virtual mockup of the case (similar to how Casetagram shows progress as photos are uploaded) as they create their case. They need to be able to crop the photos the way Casetagram does. - SEO is very important to us. Tweaking the SEO on our end will be an important necessary feature, so it'll need to be possible of us to edit page descriptions, titles, meta tags, image alt tags, headlines, etc. - We would also like to fetch live FedEx/UPS/USPS shipping rates for our customers to select or at least have us select preset shipping rates for each carrier. We will also need this to integrate into an easy to manage system for us to download out their shipping label within our system and keep the orders together within the admin panel.