The layer the game object is in. A layer is in the range [0…31].
We need more.Is it any way?
No, because the layers are represented by an integer bit-mask. An integer is made up by 4 bytes a 8 bit == 32 bit. You can’t add or remove bits it’s more like a hardware (or hardcoded) limit 
I can’t imagine any usecase where i would need more than 32 (or even 24 since 8 are predefined) layers. Maybe you can describe your problem and we find an alternative.
In regards to your comments in Bunny83’s post:
You need a custom color shader to make this work, if that’s what you’re looking for.
With such a shader, you can have a normal diffuse texture + a color mask texture. The color mask texture would have 4 channels (R, G, B and A) for up to 4 different color areas.
Let’s say you want the first part of your armor to be color 1, then you’d have to paint all the areas in red (the R channel in RGB). And a second area with blue (B channel) etc.
Then in the inspector you can set up a color and this color will be applied on the marked areas.
There is a tutorial for Strumpy Shader Editor 4.0 on how to make a color shader.
http://www.derekmbest.com/shaders.html
It’s not very good in terms of performance and it it has some flaws (i.e with the 4th color), but it should be good enough to give you an idea. I’ve recently made my own shader, took me whole three days to get it done (because I have/had zero experience about shaders), but works flawlessly now
No, it’s not possible to have more than 32 layers.