I’ve noticed that the downside of a plane, as well as the inside of an object, is not textured but transparent. Is there any way to have it textured as well? Like if I want to make a fence or a vine or something like that, that’s composed of a 2D-texture on a plane, I want the reverse side to show the same texture, only mirrored for that fake-3D-feel.
There are a couple of things you can do.
One is to use a shader that shows both faces of a model (via Cull Off command in shaderlab). For example, VegetationVertexLit one on the unify wiki.
The other thing is to actually model both sides of your model. If it’s a fence, create polygons for one side and separate polygons for the other side. This has the advantage that on both sides the lighting will be correct.
Then, how about this question.
Is it possible to make a billboard that is facing ALL cameras, rather than a specific one.
For let’s say a split screen game.
To my knowledge there’s no way to make a billboard out of a plane that faces more than one direction simultneously, short of creating multiple objects and hiding one from the other camera etc… that would ber supercomplicated.
However, I think a LineRenderer may work for this. Set the two positions to the top and bottom bounds of the object, turn off World Space and the width to the width of the object. Of course, set the material to your billboard texture. It should autoface every camera.
Or you could orient the billboard inside OnPreRender. Note however that OnPreRender is called on scripts attached to the camera, so you’d have to attach some sort of “orient my billboards” script to each camera and let them know which billboard(s) to orient.
Ah, I misunderstood how OnPreRender worked. 
Still, were I in his place, I’d go with the LineRenderer. No scripting.
That sounds a bit above my level of expertise, but I’ll experiment with it as soon as I get a chance.
Overcoming challenges is to mature.
Thanks for the tips.