From here, there are a number of things you can do.
If you want it to look a little more professional looking than a cardboard box, it's easy to cover the exposed cardboard with plain white paper or whatever else you might desire. It is best to do this when you have the cardboard box flattened.
If you're up to some lighting experimentation, it is very easy to make more softboxes with different colored and textured cloth in front, or even just color them yourself for exactly the effect you want, with watercolor or other sources of pigment.
You can also vary the position of the lighting source within the box, which will change the manner in which the light diffuse.
By all means, play around with the design. It's easily made and just as easily customizable, so it's simple to come up with just the right design to fit your specific needs.