That's a cool solution in my opinion because it matches these criteria:
- OS independent
- future-proof
- language independent
- resolution-independent (if the icon has a high enough resolution)
The point is for me if a transparent cube suits most user or better the example with the car where we have images at the cube.
In general with a full word we cannot find a solution suitable for everybody just because of the different word lengths in different languages.
Here are 2 other alternatives I see that would also fulfill the above criteria
- use dots. The cube becomes a dice.
- use two letters. So the cube would be labeled in English as Fr, Le, Ri, Re, Bo, To