For each product you build, we prebuild up to 5 framed or 10 unframed templates. You may see less than that number of templates depending on what sizes you offer of that product. For example, we may have a prebuilt template that has 16x20 and 20x24 products but you don't have the 20x24 size for a product. So that template will not be accessible as a prebuilt template because we don't want you selling that template without all the sizes.
To add more sizes to a product, click Products > Manage Products > Edit for the product you want to edit sizes for....
Now click Manage Sizes and Prices, and add (or delete) any sizes you'd like.
Don't forget to save any changes!
Also, remember, you can import templates as well!