Let's assume you have 10 designs. Let's call them 1001, 1002, 1003 and so on.
Every design might be available for various types of products.
For example, let's assume that a design called '1001' is available for phone cases, mouse pads, notebooks, men's t-shirts and women's t-shirts.
The total number of design files that have to be created are 5 (1 for every type of product as they are all sized differently).
For all the models of phone cases, only one ODF is enough since it is a combination of all the phone sizes. Learn more about the ODF here.
Thus, the naming convention to be followed for design '1001' would be
1001PC - Phone Case
1001NB - Notebooks
1001MUG - Mugs and so on.
You can prefix this design code with anything you want. Like the artist/brand name.
For example - PT1001PC
Please avoid using the same design number i.e 1001 for two different designs to avoid duplication and errors.