Nice maps and useful to others I would think.
The lightness thing is hard. All monitors have different set up and unless they are calibrated then its going to look different on each. I agree with Steel that some maps like some of Ascensions seem very dark to me too and many people who have copied the style have produced similarly dark maps so there must be some popularity to it.
So I wouldn't get too concerned with it. You set it up how your monitor makes them look best. I just brighten up an image thats too dark for me. Ok so I loose a bit of dynamic range in them but thats not a big loss. Oh for a time when we all work in RGB 16,16,16 or even more spectral colors as well.