[(E)]

I suppose I am looking for lists of planes for the purpose of finding commonalities and themes. There are already broad categories evident in the lists people have provided. Hells, Divine realms, intellectual concepts and so forth.

The bards tale books throws another couple in like the checkered fields a realm where gods do battle.

The "rabbit hole" realms are potentially a side issue to do with how the realms/planes are accessed.

The Dungeon dimensions are another one that leaps to mind that might be considered a meta example.

Edit
As to the second part of the question, planes/realms that are implied by gurps. First up the question might be better phrased as "What extra planes of existence are implied by gurps rules?". An earlier post pointed out that demons etc don't need to come from another plane of existence, this is a valid point and I don't challenge it. However for the point of this thread let's assume all the internal gurps system/setting switches are set to "more planes of existence". Using that as a (re)start point what dimensions does a setting built to be compatability with the various magic/path/dungeon fantasy gurps rules have to include?