Billboard help on Rock Ceiling!

[CarnivorousJelly]

So, Uhm yeah everyone knows here that i suck at billboards.
I need to make something really realistic and i need help on it.
Here are some screenshots.
<images>
Can someone give me advise with these billboards?
Thanks.

1. Connect them to a pointlight (this pointlight should be a very dark version of the colour coming through the hole in the ceiling). This will make changing the colours later on a lot easier. If you already have them connected to a pointlight, never mind this. If you don't know how to do this, let me know so I can explain further :)

2. Make sure they all reach very close to the ground, around the edge of the light cast by your spotlight (they should form a slight cone). They shouldn't actually touch the ground or clip through it, though.

3. Start with a general outline of the shape created by the hole (you already have most of this), then fill in the sharp corners and gaps with more billboards (like this which ends up looking like this when the colour is changed to not blue).

4. Place an AXIS billboard (not a fixed axis) in the very center that's dimmer than the rest of the billboards. Set it to "Halo" so it doesn't look weird when you walk through the billboards. This will act as a bloom of light.

5. Make all the billboards about 1/4 as bright as they currently are. "Billboards" are created when light illuminates tiny particles of dust in the air. It would take a lot of dust to make them that bright and thick looking.