Correction about link-local: v6 link-local doesn't really work for this - LL addresses are meant to be used for low level stuff like address autoconfiguration and neighbour discovery. They don't even work with the normal socket APIs without doing some extra gymnastics (specifying interface indices etc).
What does work though is ULA (Unique Local Addresses) - they're also designed to prevent conflicts when you eventually end up making a mashup of your and someone else's network who also wanted to use their own addresses.
What does work though is ULA (Unique Local Addresses) - they're also designed to prevent conflicts when you eventually end up making a mashup of your and someone else's network who also wanted to use their own addresses.