Crash report:
[media]So I created a new superflat world in creative mode, this time with grass as the main block. On the grass, I could easily tame a llama, and see inside of its inventory. I then filled in a large area with glass (100x100). On this glass layer (white stained glass) I could not tame the llama, nor did it wander or boot me off like normal when I got on rode it. This only works with different types of glass (only tested white stained glass and normal glass though).
Edit: This also applies to leaves
I took the spawn eggs out of the creative inventory. I also set a few gamerules such as doDaylightCycle and doWeatherCycle to false, but I can't see how that would affect anything.
I just tested a few other non-spawnable blocks. All other blocks that I tested besides leaves and glass seem to allow llama taming. I only tested a select few to try to find correlation between non-spawnable blocks and llama breeding but it seems that there is none.
The blocks I tested are:
Carpets
Top slabs
end portal frames
mob spawners
All of these blocks seemed to have no issues with llama taming; however, both glass and leaves still do for some reason.