Jonas your spark plug in the first pictures are really only showing USED...
To get a idea on how the spark plug is doing you must start off with a new spark plug. Then carry your tools used to change spark plug and off on a drive. You can and should bring a couple or at least one more new spark plug with you. Once the engine is completely up to all operating temperatures find a nice straight road that you are also able to pull over and safely to pull a spark plug. SO the next decision is where you want to find out what the spark plug is doing. Your choice can be, best fuel economy, idle speed. idle speed using the AC on , city or stop and go traffic etc.
Let give you and example but to understand why this procedure is the only and best way to read any spark plug. First and foremost the bad thing is 99.999% of people read their spark plugs after the engine has idled down. This is the worst way to read a plug. Idle speeds and ECU adjustments are totally and completely different then any other engine speeds and loads. The spark plug will almost never give a good impression what they are doing only the generalized old comparing spark plug charts that most show the best and worst conditions of a spark plug. You pictures really show several variation on what is going on in the combustion chamber and the condition of the engine. So many of the the responses are accurate but not conclusive of the bigger picture of performance accuracy.
Going back to reading a spark plug. So lets say you want to see how the spark plug is support your MPG at highway speeds. This is were you need to read carefully how to do it correctly because it is also how you perform the test to read any engine speed spark readings. You first get to the common speed at which you drive on the highway and maintain it for about a mile or 2. At some point without changing your throttle position turn off the engine and safely pull over off the road and come to a stop. By turning of the engine and not changing the throttle position your spark plug is firing exactly as it would be at the engine speed and load. So when you pull any spark plug from any cylinder how it looks is giving you how the spark plug is firing in that cylinder. Now you can pull one or all of them but I would take pictures and make notes of engine speed(rpm) and mph. Coolant temperatures, IAT timing values etc. are all even better to collect but not necessary for a generalized impression of the spark plugs performance at your choice of set driving conditions you established to test.
You can also for fun take any of those spark plugs you pictured and do a power pull test. This is do in 2 steps. The first is a cleaning run. A cleaning run will be to accurate hard for about 1/8 mile and do the same shut down and pull over procedure. Remove the easiest spark plug look at it take pictures. then reinstall it. During your first run the engine may hesitate and even misfire this is normal and expected given the condition of your spark plugs pictured. Now do a second run the same way and pull and inspect the spark plug. You may notice that the spark plug looks very different from the pictures you posted. And the engine is likely not to miss fire or hesitate. You might even do one more final run and inspect? Don't be surprise if the engine runs better idles better and spark plug look noticeably better then what was in your first pictures.
This procedure is not new nor is it of my invention so to say. Performance engine builder and racers know that the last and PIA thing to do is to find the best spark plug type, heat range and gap for an engine. It takes hours to do this. For a street vehicle the benefits are seeing and getting a better idea what the spark plugs are actually doing. Also if more did proper spark plug evaluation they might find that changing spark plug more often has more benefits and that you do not need high dollar specials coated or design spark plugs.
I will say I am happy that indexing a spark plug is no longer a task I need to do anymore except a couple of my older Motorcycles.
But any of my Nitorus fed engines are always a challenge.
and multiple carburetors are the worst..... 
