Thanks for the feedback, people!
So just for fun I had a go at adding the light beams in in photoshop. 3D modeling may still be beyond me, but I like to think I'm alright in 2D. IMHO I think the top right light beams came out alright, but the cone on the right and the blue area on the left definitely aren't great. Obviously being a test render I didn't want to waste a whole lot of time on it, but I thought I'd give it a shot. Yay? Nay?
So... I think "Yay", and thanks for giving it a shot
Indeed the top right beams are alright. If I cannot get a decent solution within Blender, I think I'll be able to safely hand my render to you for post-processing, which isn't really my forte.
Just letting you know: these light beams in the top right corner are meant to be on a proper "background layer", whereas the other beams of light (such as the yellow-greenish on the right and the purple one on the left) are on a separate "light" layers which would have to be made by post-processing (compositing within Blender, or Photoshop on your end). You can learn more about how the fields are layered if you open a field file using Palmer. In any case, I can guide you through whatever post-processing which would need to be done.
Most of the original backgrounds had been edited in an image editor.
That's true, and there's more. Pretty much any advanced CG art has some post-processing to it. It's actually recommended practice.
Correct me if I'm wrong, but I believe that the glow around the bulbs and the rays of light are essentially the same idea, which is volumetric lighting. It's something that's only recently been introduced to Blender/Cycles in the form of Volumetric shaders. I don't think it gives true volumetric lighting, but there are ways of faking it I think, which is what I believe Mayo is struggling with.
Again my knowledge of 3D is spotty, but I think that's the gist of it. Once I get a job and can afford to upgrade my rig, then I'm gonna invest some time in actually learning this stuff. 
As far as I'm aware, Blender doesn't really have a volumetric emission of light, and I'm not sure how to mimic this. Blender has a very nice volume scattering shader, but I was unable to use this shader in order to create the intended "light beam" effect, mostly for 2 reasons:
1- If you define a volume with many light scatterers in it, the density of scatterers is isotropic in the volume. Thus, it is difficult to have a lateral "fading" of the beam of light, and the result really feels unnatural.
2- The volume of scatterers will scatter all the light sources. Given the multiple light sources in my scene, this makes a weird result.
Maybe there's a solution out there, but I haven't found it.
Now, the light around the bulbs or just surrounding lamps are (in my opinion) a different effect - although the cause (scattering) may be similar. Often, we're talking about glow, or glare effects. These are meant to be done by post-processing, so it will be best if I leave these to you, as well. I'm not sure Blender users have tried to replicate glare effects by means of shaders, but I believe it would be overly complicated while it can be made easily via post-processing.
All in all: I'll keep investigating for solutions on my end, but I'll be sure to contact you when it comes to do the post-processing.
My problem is that the design of ealin(?) is entirely against Aerith statement that the church is the only place where flowers grow in Midgar. Also from where is the lighting coming?
I'm assuming you're referring to the field file describing the outdoors of Aerith's (and Elmyra's) house. As for "where is the lighting coming", I've always assumed it was daylight, which could be explained by a combination of
a/the house being located at the periphery of the city
b/ the Plate construction being incomplete in some parts
As for the Flowers question: the presence of flowers can be explained from two angles, in my opinion:
- One angle is rather "symbolic": Aerith is a special character, her Cetra lineage grants her particular powers, such as "interacting with the Planet" (sure, it's a pretty vague term). The presence of flowers where Aerith lives symbolizes this interaction, in my view.
- One angle is more pragmatic: Aerith loves flowers, which only grew originally at the Church. She could have perfectly transplanted some in the backyard of her home (you'll notice there's plenty of water around, besides).
Well, that's my take on it. At least it allows for reconciling what she says with how the environment is like.
