Roman said:
BTW: I see how you are tinkering with space, but how would you tinker with time, life (this one sounds the most difficult) and magic?
Well, the time-tinkering

is somewhat suggested in Manual of the Planes. If you have different planes advance slower or faster in time (with the PCs when they're there), creating a "shift" between them, you can have interesting consequences on adventures.
E.g. the characters may use a "fast" plane to go and rest a whole day (getting spells and healing) while only an hour passes in their world. Or they may banish a powerful foe into a "slow" plane so that when he comes back, 20 years have passed for them (but 20 days for him) and they are much higher level now
Nonetheless, these are dangerous things to do, as abuse of this sort of trick can easily disrupt a campaign, not to mention if there are "reverse-timed" planes which could allow the group to go back in time! I personally like these ideas but I've never used them because of these dangers.
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The life-tinkering I was thinking about is simply the "rules of life" about creatures native to different planes, which sometimes could be inherent to the plane instead of to the creatures.
Mortals (creatures of material planes) are born, grow up, eat/drink/breathe/reproduce/etc, and die. You can set details about non-mortals in different ways. Two examples I usually follow:
I tend to play Elementals so that they form spontaneously from their plane or from a "pool" of that element on another plane, with a currently strong connection with the original elemental plane. When slain or simply after some time, these creatures merge with their element again and "dissipate". They aren't after all really separate from the element as a whole. While they are temporarily individuals, these creatures may for instance grow if "fed" with their own element, and some of them may mimicked mortal life forms and "simulate" even a sort of breeding: you may see fire tigers mate and make offspring, but it's just a mockery. This I explain with the fact that, while elemental planes "power" the material planes with energy, they are "feedback-ed" shapes from those material planes which they try to mimick.
Just to make it different, shadow creatures are quite similar in the sense that they aren't really separate from the plane of shadows, but the "feedback" is much stronger: for every creature in the material plane there is exactly one correspondent shadow creature in the plane of shadows (undead shadows are more complicated however...). Other than the 1:1 rate, there's no other link between the two: the shadow of an elf is not necessarily a shadow-elf, it could be anything. If the material creature dies, the shadow creature merges with shadow. If you kill a shadow creature, no problem, another one forms somewhere else to keep the rate (no harm to the "correspondent" material creature).
What is interesting is that every time a material creature goes to the plane of shadow, the current correspondent shadow may come out of it and wreck havoc in the material world; the scholars who believe in this theory strongly advocate never to use Shadow walk or similar spells. (this whole idea would work great with a Plane of Mirror if you use it)
Then there's different life rules on some planes. The famous example is Ysgard, a place where it is almost impossible to die because next die you automatically resurrect. IIRC you are also constantly healed of wounds. The consequence is that Ysgard is the "warrior's heaven" where everyone who loved battle can keep hacking each others without actually hurting anyone.
Other consequences: violence on Ysgard isn't seen as a crime; destroying someone's stuff, house or equipment is a capital offense (since objects aren't "resurrected").
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Tinkering with magic means to alter how spellcasting works. The possibilities are near-endless... you can hamper or prohibit some types of spells, empower other types, grant inborn magic abilities to any native or even to the visitors.
For example, IMC I planned to have Arcadia as an alternate material plane infused with magic: everyone who's lived long enough there could freely cast a cantrip or two (randomly determined), creation magic and other arcane spells find themselves improved.
In this place, towns and cities are quickly rebuilt or simply readjusted by the people when they're tired by their house's setup, and destroying someone's property only causes the annoyance of spending a few minutes/hours to build it back.
OTOH divine spellcasting isn't improved and so life threats are seriously taken here.
Finally, you can add randomness to magic. That is usually more complicated to run, and tends to make players more careful, often resulting in them casting more rarely.