I should clarify.  West End Games did a lot of world(s) building.  Dathomir was set aside as being a primitive world rich with force users and, as a result, a blockade was placed around the planet by the Emperor and the planet forbidden.  The final note, somewhat tongue-in-cheek, was that it could be the world where your fantasy characters dwelt.

Another interesting bit of note was Ryloth.  The Twi'lekki were more interesting there.  The authors looked at Bib-Fortuna and Oola and made some observations and determined that they were likely underground dwellers like naked mole rats.  They had no hair because they had no need of it.  Their head tentacles were sensitive to vibration and served well in situations where one could not see.  They then speculated on a reason for them to live underground and reasoned that Ryloth was a tidally locked planet, one side too hot and one side too cold with only a thin band of terrain suitable for surface living.