Overseer was pretty good, I suspect it works with 31.18 by now. It's a bit like Visual Fortress from the older versions, but compatible with more things. Still a work-in-progress, last I checked it didn't have water yet but they might have done that by now.
I might have been running it on low quality when I took that picture. Search the General Discussion forum for it.
There's also Stonesense, which I don't like but mainly because it's not very good for taking really big pictures.
Stonesense is actually pretty good for taking big pictures; it's just that the pictures are, well, really big. For example, I recently uploaded an embark location to show off the two 150+ z-levels tall spire-mountains spearing up from the glacier:
http://img.ie/2ba36.png.htmlClick the pic for it's true size: 4608x5652 (it's like XBOX HUEG).
To take pictures like this, you have to do a few things. Firstly, to increase the z-level depth shown, either hold control and scroll down with the mouse, or go into the init.txt and edit the line that says [SEGMENTSIZE:x], so that the "x" is the z-levels you need.
Then navigate in Stonesense to where you want to take the picture, and hit Ctrl+F5, which captures the entire map. Hitting F2 beforehand clears away the overlays to make it screenshot-friendly.
Keep in mind that at my current knowledge, both Overseer and Stonesense need to have the Memory.xml from the latest dfhack set to be compatible with 31.18, and Stonesense will not depict creatures with it (thus why there are no dwarves near the wagon in the above image)