okay, I took all your suggestions into account carnivac, should be OK now.
I also made another part - with a bit from my personal knowledge treasure.

links: (if the images don't work)

Link Part 1

Great stuff!
Although it might be a bit complicated to someone new to the concept and all the terms..
Having the tutorial split into a simple basics part and then a more advanced in-depth part would be best.

I also agree that it's fun to break the rules and add in weird perspectives that do not actually make sense.
Just like A link to the Past or Minish Cap..
Because otherwise everything usually looks extremely square and straight, which can be quite boring.

But to break the rules you first need to learn how to follow them

there are a bunch of very basic terms which everybody should know I guess. But however, it's maybe necessary to get an overview first and why we use these established perspectives. I think it's necessary to recognize the difference between 3D iso and 2.5D iso. 45° (ultima), other axonometrics (e.g. 180 - 60) are dead.
more important than looking straight and flat is the hiding of the tile grid. E.g. SD3 was pretty good with hiding it and it looks beautiful although the environment graphics are done without breaking the rules often.

Because of this I made another part with some very popular examples and explaining some very basic terms. This time I also used a text tool. Looks a bit more professional than my handwriting. Maybe It'd be also a good idea to overwork the other part later, maybe I'll do this if there is time. I also think that we need at least one example more to make it really convincing. I am thinking of a treasure chest, which is simple enough to imagine but hard enough for a beginner to construct and to learn the basics.

If I am right the other themes (apart from the trees) we also have very often here are "the" grass tile and creating human bases for RPGs

Here the part I made today:
-posted an edited version below -

Credits:
The font is from Joschua Sauer's "Nicht Lustig" cartoons/page.
Also credits to all the artists who created the graphics of the examples

P.S.: @Helm: you posted tons good stuff here and I learnt really a lot from you so far - especially as I started with pixels, so I think it's good that I can finally contribute something to pixelation.

Should be self-explaining...

I am not trying to sync the monitors (@ facet). I know the Laptop monitor is by far weaker than the extern monitor. As the moment it's nice to compare the impression (@blumunkee). The site you posted seems to be pretty nice and I definitely have to check it out (@ai)

The main problem I spotted so far is that I simple don't know what's right and what's wrong with the calibration. FOr example with the HSV color system it's at the moment hard for me to tell the difference between 0 (pure black) and 20 - they all seem to be pretty dark compared to light tones, and if there is a slight gradient between 5-10 it's hard to tell that here is a gradient. I tried different calibarations and all have their own advantages and disadvantages - the really bad thing is that it's also impossible to make sure that the colors of the images you are create are looking good on any monitor. I don't checked out the site and  maybe it'll help me, but the big question for me is if it's even worth to think about this (have oyou ever asked yourself similar questions?) or if I simple have to invest money in a new and professional extern monitor to make sure that my result will look good on other monitors too.