Rather than try and explain what's going on I'll start by pointing you at my Using 3D nodes (Cellular) with 2D UV maps ? topic on the Poser Technical forum here at Renderosity. You'll notice that the more-or-less final shader that I ended up with over there has the three fBm nodes (which are in the "Creates three random greyscale tilings" chunk of the annotated shader above) plugged directly into the User_Defined node that creates the tile colours (which is the middle node near the left edge of the annotated shader above).

So basically all the junk and spaghetti in between is just for those weights !

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The 3Dcheapskate* occasionally posts sensible stuff. Usually by accident.
And it usually uses Poser 11, with units set to inches. Except when it's using Poser 6 or PP2014, or when its units are set to PNU.

*also available in ShareCG, DAZ, and HiveWire3D flavours (the DeviantArt and CGBytes flavour have been discontinued).