First,
If such a product already exists, please forgive me, and if you would be so kind point to where it is!
This is going to sound odd, but sometimes I wish a had a good map for another plane of existence. If I was envisioning a custom made flip-mat and I didn't have to worry about it being too crazy or frivolous..
I would want one side to represent a scene that I could use to depict Golarion's Boneyard. I realize GameMastery products tend to be generic for usability to GMs who don't use Golarion, so perhaps some otherworldly landscape where the throne of some unspecified deity is depicted.
On the other side, perhaps something like the ethereal plane or Limbo where islands of matter float.. like on the cover of Bestiary 2. This could be a handy all purpose map.
Why would I want a map that featured a deity's throne / or the Boneyard? Because in my game when players die, they got to the Boneyard and await judgment. When they are the subject of a raise dead spell or resurrection they are pulled from there back across the River of Souls. Sometimes I run entire short encounters there with psychopomps and other outsiders. Sometimes entire adventures spring from what happens in the Boneyard.
This may be too exotic or extravagant for a flip-mat, but there is no harm in spitballing ideas. :)