Cubeast - Limiting Myself While Designing/Modeling

So, for practice, i set 3 rules while concepting/modeling this one:

1 - I must use a cube as base for a sci fi vehicle. I can't modify the cube.
2 - No to too much detail. So i can't drown the cube
3 - No hand painting, texturing, decals etc.

While it was a fun practice, last one made it harder than i expected.