Only common SKU properties are available immediately, as the SKUName, SKUDescription, etc. fields.
You would need to create a macro method to lookup for all Pages/documents that have the NodeSKUID equal to the SKUID. In most cases this gives you single node, or you can achieve it by using .First macro selector over the collection of results or similar...
The ShoppingCart.ShoppingCartItems macro actually accesses the collection of shopping cart items, it doesn't render them in any way, unless you access a string (or other) property of one member of that collection or if you use ApplyTransformation over the collection to transform the objects into displayable markup. More on this topic can be found at
Using transformations in macro expressions documentation article.
Moreover, besides ShoppingCart object, you could use Order object in the order invoice template...
Should you need any additional details, please feel free to ask.