Compositing with multiple renderers
Put every 3D geometries inside a composition to multiply it's renderers
Select the 3 geometries we already created and press Ctrl+shift+C to put them inside a composition (I'll rename this composition "3D compo")
You can also do it by selecting your 3 geometries and Right Click > Make Compo
Now select this "3D compo" composition and either Right Click > Add Renderer or press Ctrl+shift+C to add a renderer on this composition.
Turn this newly created renderer in "perspective placement". This placement type will allow you to deform your image to adapt it to a different perspective.
How to manipulate a "Perspective" 2D renderer
Now go in edit mode (red circle on the screenshot below) and select the perspective placement renderer. Now you can use the little green points on the corner of the layer to move and distort the image. I placed this second renderer as showed on the screenshot below with a 25% opacity.
You can either place it with your hands or copy "Position A/B/C/D" of the renderer's parameter if you want to copy it exactly.
You can like that multiply the renderer with a very few performances cost and so render complex and detailed environments using this technique and your imagination.
Add fancy effects
Let's add a Fake AA blur : Right Click > Modifiers>Blur>Blur>FakeAA
This will just smooth the image a little bit as for now volumetric Light is not compatible with AA. If you go see in "Fake AA" parameters you'll see that it is a blur made of 4 samples (Size) on the same resolution than the sampled image (Down Sampling) and each of theses samples are spaced by 0.5px (Base size). And all of theses samples are scattered accordingly to a Gaussian algorithm.
Add now a "Add contrast+" Exposure modifier preset Right Click > Modifiers>Color>Exposure>Add contrast +
And put a vignet radial mask over the exposure modifier: Right Click > Masks>Radial Mask>Vignet
Now uncheck the "Inverse" Parameter of the radial Mask and go in edit mode (green circle) to place it with your own little hands or just reproduce the values in your keyboard.
And to finish it off, Add a Chromatic Abberation Right Click > Modifiers>Stylize>Chromatic Aberration
I really don't know what conclusion I could make from all of this....
Oh yeah, for thoses who find that composition too dark, you can add this little omni light next to the others (and don't forget to disactivate it's volumetric as we saw before)
and here what you will get :