Marco, that last one is particularly good.
When I posted upthread about the VMS textures (especially the central rosette) perhaps being explicitly earth/air/fire/water, one of the problems was trying to ascertain which was which. Pipes could be air (nothing is coming out of the ones in the center rosette) or they could be water (water flows through pipes). The dotted texture also could be either air or water.
The scalloped shapes I've always suspected might be earth and the flame-like shapes I've always suspected might be fire, but just as the "elements" diagram earlier in the VMS (assuming its elements or humors or something along those lines) have a couple that seem almost deliberately ambiguous, and so do the rosettes.
But that last image you depicted, with the "rocks" (the scalloped texture) heaped up in piles with the flames coming out of them, when presented in that way, are reminiscent of volcanoes, which represent both earth and fire, and I wonder if that is what inspired the odd medieval diagrams of things like look like piles of rocks. Volcanoes aren't exactly piles of rocks, but in classical and medieval society once something is drawn that way, it gets copied that way, so perhaps that's why we see "piles of rocks" on the edges of medieval cosmological diagrams.
In fact, in some ways, one could take it a step farther. Hildegard von Bingen was the kind of person who saw things in interesting ways as apparently did the author of the VMS and maybe she and perhaps the VMS author saw volcanoes as the embodiment of all the elements. They have earth, they have fire, they have air (the hot vapors that escape even before there is an eruption) and they have "water" (liquid) in the form of both steam and lava.
So in some diagrams, maybe that heap of stones isn't just earth, or earth and fire when it has red flames coming out of it, maybe in some cases it means earth/air/water/fire or earth and something else (since air, fire, water, and earth all spew from volcanoes). In other words, if something is coming out of a volcano-like triangular heap of rocks in the VMS, it doesn't automatically have to be fire, it could be any of the elements which would make it a little easier to interpret the round dots as not necessarily being fire, but still being similar to those other medieval drawings in concept.
You know, until I looked at the last drawing you posted (with the heaps and flames), I never thought of volcanoes as the iconic embodiment of all the elements but in a sense, they are and it also occurred to me if you simply drew it as a triangle (to mean mountain), it would be hard to tell what it is, but if you drew it as a heap of rocks, it would be recognizable (active volcanoes always have stuff strewn all over their banks from previous eruptions).
I also noticed some visual similarities between this, the VMS, and some zodiac imagery (the similarities are not necessarily direct in terms of meaning, but possibly in terms of thematic medieval representation):