Can I choose different shapes for the MC2 Molecube?

It's not possible to compose your own Molecube.

There are 13 sets available ranging from 2-4-6-8 and even 10 cubes! The cabinets and shelves are available in 7 different colors! Pick the color shelve you'd like for your Molecube and mix and match the cabinets. You have plenty of space to style your Molecube with your personal items!