Cool!
For that style of picture you want to make, here's an overview of what you could do:
- Create the shape(s) you want to use.
- Create background plane.
- Move camera into desired position.
- Move shape out of camera view.
- Make the plane a particle emitter.
- Select the shape(s) as the particles.
- Set up density, size, and rotation randomness of the particles.
- Set up lighting, materials, and depth of field.
- Set the timeline to some position other than 0 to have particles emit
- Render!
Sorry that I can't go into more detail, but I have things to do. I think you should be able to find tutorials for any individual things I mentioned, though.
Also, to make that shape, simply create a cube, go into edit mode, go into face selection mode, hit "a" to select all the faces, subdivide it once, then select the four top corners of the cube, and hit alt+m (select center in the pop-up). Repeat the alt+m merge for the bottom.
