Images in 3d view have space between each other

Try changing the blending mode of all six layers that make up the cube to Alpha Add. This reduces the aliasing problem when the layers do not perfectly align with the pixel grid. 

The problem happens because the edges of the layers do not perfectly line up with the pixel grid when they are rotated in 3D space. 3D layers also have no Z depth. Create a 400 X 400 solid, make it 3D, rotate 90º in X, duplicate the layer, and change the Z anchor point from zero to 1 on one of the layers. Magnify the comp as much as possible, and you will not see any pixels. You'll have to move the layer off from the comp center about 5 pixels before seeing an antialiased line of pixels start to show up.

The best-looking solution is to change the blending mode to Alpha Add, then add an Adjustment layer with CC Motion Blur applied. Check out the sample comp I uploaded. Take a look at these screenshots.