It would be interesting to know more. A couple of things that you should also consider are :
1. The Categories- What precisely would you like a user to do/design ? In this specific example , the categories are a little broad (wearables - furniture). What you need for 3D furniture design and rendering on a mobile interface may differ vastly from what you need to design a wearable (Eg. customizable t-shirt). Starting with a couple of related categories would help narrow down requirements better.
2. Purpose and execution : What exactly would you like the user to do finally? Would it be to submit designs which could then be converted as retail products? Who makes these designs? Things like t-shirts are a lot simpler - a design could include color, size, text/graphic. A piece of furniture is vastly different and it might need expertise from a user standpoint . Which kind of people and products would it (the app) truly work for?