Notice how the edges are round? It doesn't look good. So what you should do now is crease all of the edges to finish off the cube!
I will show you how to make an origami paper cube in less than 3 minutes. These paper cubes are really fun to make! After you finish making the cube, you could also try putting a LED inside the cube to make awesome lighting effects! Credit for the LED in the cube goes to gorillazmiko.