Romulus your method would work great if I hadn’t set everything up with real world uvs haha. But im glad there’s interest in this!
Real world scale is not an obstacle, because it’s just a scale, it doesn’t change anything. You just need to multiply tiles count by your fabric texture RW size and you will get exactly the same result. If your fabric has 50 by 50 cm RW size and you want 10 unique patches, you just need to set tiles to 500 by 500 cm RW size.
Ah very good point!
This is a surprisingly hard task! 
One thing I can think of is making the texture tiles dependent on the geometry faces. So for example if the fabric is supposed to be 10x10 tiles, the object would be a plane with 10x10 faces. Then you could use things like 3ds Max MaterialByElement modifier with Multimap’s randomization by Material ID. Or the V8 randomization by polygon.
But if the fabric’s geometry is independent from the texture tiling, it really gets tricky.
What I imagine here would be some kind of UVW Randomizer merged with Multimap node. Or Multimap randomization mode “By UVW Randomizer tiles”.
I’ll log it as a general feature request with a simple example and we will see what can be done about it.
(Report ID=CRMAX-1006)
I would love to see this evolving in to Corona Tiles ;]