You can make all kinds of designs, perhaps pretending that you are making an animal or an alien or designing a house or some futuristic building or in fact you can just imagine that you are creating rather interesting shapes and are happy with that.
It is quite a good idea to set some sort of rule or rulesthat you have to follow and see how many models/designs you can make if you follow those rules.
I think a good challenge to start with is;
Now let's say that the cubes have to be joined "properly", that is with no twists, so a that a square face is flat against the next square face.
So the two main rules that will control how we will build are as follows:-
Well I wonder how many different designs you can discover or forecast?
Unless you have lots and lots, I really mean lots, of these cubes to use you will have to make a record of what you have done each time. This can be useful so that you can check that you have not done the same ones twice.
When you've done a few it would be good to see if there is a "system", or "particular way of working" that you are using or could use to make things easier.