The whole lab including enchanted items has been posted on the forums for almost three years now. The single biggest contributor is Refinement (adds +7 Safety in my lab). If you have appropriate craftsmen as part of the Covenant then you can get Superior Tools and Superior Equipment without the increased Upkeep, which also adds +2 Safety. If the building the lab is in is created by magic you can get Superior Construction which is another +1 Safety. Servant is a cheap way to get a bonus to Safety.
The examples are good for showing a broad range of options but all but one have +0 or +1 Refinement, several have a LOT of Size which is detrimental to Safety, and things like Decaying/Damp/Lightless which would rarely be taken in play are very common.
-1: Decaying and no improvements. Not a Lab most Magi would ever use.
0: Decaying, Lightless, little improvement. A "scary" lab, for the beginning Perdo specialist who wants that. Working in it would be difficult.
-7: A ruin abandoned for a long time. Damp, Decaying, Uneven Floor, Unstable, Vulnerable, Wreaked, etc. Not something you will see as a Magi's lab in play.
0: Visitor labs with drawbacks. Cramped is -2 Safety and not something you will often find in personal labs.
0: Disorganized, which is the opposite of what you will often find (Highly Organized). With a little work this would be a fine lab for a Herbam specialist though.
+1: Size +6 (!!!) and only Refinement +3 for an Archmagus lab?! It is designed specifically to get high Aesthetics (+15) rather than being a working lab.
0: This is a field lab, rather than one at a Covenant. Good example of setting up something at a site to study it though.
-2: Another lab that could be described as a field lab. It is just setup in a cave with no improvements. It has Health -8 which is like living in a garbage dump. It will cut 40 years off a Magi's lifespan.
-3: Poor quality everything, infested with webs, low ceiling and uneven floor, bad heating and lighting. For almost any task this lab is worse than a default all 0 lab.
Almost all the examples seem to go for flavor, picking really out there combinations and lots of flaws. Half are ether decaying messes or a rough field lab. All but the Archmagi's have little to no Refinement. None are a good example of what you will generally see in play.