Although I haven’t done that much of it – I do enjoy writing about Alternate Realities. It always seems to me that anything goes and there is absolutely no constraint on one’s imagination.
In a short story The Southampton Reality I wrote about a pocket alternate reality that had been constructed by a highly advanced alien race and then left as a failed experiment. It was quietly overseen by the alternate reality police (from the Central Reality) to ensure that it’s unusual residents didn’t have undue (take that as any) interaction with occasional accidental visitors from other realities.
In the Sky is the Wrong Colour- I wrote about an airport type facility where displaced visitors from other realities could (sort of) dial home (if they knew how to). The size of the facility hinted at a large amount of traffic but when an aircraft from our own reality inadvertently lands, the whole facility is eerily empty.
Currently I’m completing a collection of short sci-fi stories for publication later this year which will include one longer story about a group of people plunged into progressively more remote alternate realities in order to lose them and the resultant rescue mission.