The internal landscape often consists of fundamental structures (walls, buildings, decorations, etc.) and functional structures (manipulable objects, magic items, portals, boxes containing "stuff" and much more).
Often the fundamental structures are just that -- basic "stuff" that cordons off areas, creates or represents internal barriers, makes time inside one's head somewhat more present. These are simply matters of convenience.
However, the functional structures in one's internal landscape can arguably be called fragments of personality. Bear with me.
For example, in my internal landscape I have a book or journal we call our "logbook." This book is used to catalog events. It is searchable, an almost magical "object" and allows us to track external time as almost a linear experience. It's our continuity and where we check up on what each other is doing, check back to where we've met people, etc. It's not always entirely accurate, and we blame that on improperly recording information in the Logbook.
However the book looks as a visual/spacial representation in our head, in function it is probably a fragment personality who, like many fragments, have a very limited identity and function. Its function is to log time and events/circumstances, catalog the people we meet and allow us to have a somewhat continual experience of Front. It is so closely tied to front that we normally find it sitting on the "control" desk (another functional structure in our head) which is directly adjacent to our Front. The times that our Logbook is out-of-sync with external reality, where pages go missing or where information is misrecorded probably represent times that the Logbook fragment is not functioning to specs; rather than other individuals in our head actively writing in the logbook, the Logbook's sole function is to track this information for us. When it malfunctions it's either due to an error in what it recorded or an error in our currently being able to access the recorded information. When we do a proper headcount, we have to count the Logbook as a fragment. It's a splinter of our overall psyche, and hence it's a fragment not a person nor really truly an object. We just view it and treat it like an object or device.
Well, firstly, this question might be better placed with the main article on Internal Landscapes written by Bob King. I'm not entirely condoning the "creation" of an internal landscape. At least in my case, the fundamental structure of my internal landscape has never changed. I have had limited success adding objects to it consciously. We did create the boardroom somewhat consciously, with the round table, the chairs...but I don't believe those are really "functional" objects in our internal landscape -- I think they're all fundamental structures, and sometimes they don't seem to be there at all. It's almost like it appears when we need it. So I think it's not a permanent structure in our internal landscape.
Some functional items were acquired through initiations in shamanic techniques (for example our experience being initiated to The Golden Cauldron healing journeys led to a Golden Cauldron being in our internal landscape), some were probably created before we were aware of our internal landscape (our Logbook, and the File Cabinet for long-term memory and informational memory being two).
The purpose of this article isn't really to create these things on-purpose. I would never recommend "creating" people in your head or fragments on purpose -- it's for recognizing different elements of your internal landscape for what they probably are. It may be helpful to realize that I can't throw out my Logbook, because it's a fragment. I can't throw out my file cabinet, no more than I can throw myself out. If I'm going to re-create the foundation of my internal landscape these fragment-metaphors need to be transformed to fit into the new paradigm/landscape. So a jungle landscape or a desert landscape -- I'd have to determine how to represent these functional items in the new space.
Perhaps you can't deliberately create a permanent landscape until you consider this. I'm not sure.