Rhein-Ruhr I once started on but never finished. It wasn't a particularly well detailed base map I was working from so it wouldn't have generated as good a result as the ones above anyway. Good maps are hard to come by and I'm more inclined to pick up the map making again if I encounter good maps showing all of the build up areas AND a scale. Lack of good source material is what made me stop doing these maps in the first place.
I do have Rhein-Main (Frankfurt) for you.
Istanbul. Rather detailed but too zoomed in...
Moscow. Overall a good map but I prefer a little more detail.
Mumbai. Good for size comparison, but lacks detail and doesn't show the greater area. This is basically just the build up area of Salsette Island (Mumbai, Thane), but not Navi Mumbai on the mainland.
Shanghai I have posted above, but not to the extend of showing a whole megalopolis. (in fact the Shanghai map is a bit too zoomed in , like the London one, I usually prefer to show more of the outlying area but good maps are hard to come by).