I'll take up the mantle of questioning here: why do dwarven engraves tend to pick their most grisly history for their art, rather than the more notable and constant gaining of wealth? Personally, I'd think as an engraver I'd want to show a mountainhome's gleaming halls of gold or whatever, not the fields of blood outside (if forced to choose only one, of course)
Dwarves pick notable
events to engrave. Could you draw a picture of the roaring twenties? The gilded age? Maybe you could, but it would be kind of hard. Now how about 9/11? Hiroshima? How about your cousin's birth, or Nelson's death at Trafalgar? With a little competency and perhaps a good reference, you could depict those all quite clearly.
Engravings, even masterful ones, have to be sparing with complexity. You don't have painted colors to tell your story, only shades of the stone you work with... and for Dwarf Fortress, you have one panel too: as of now, there are no multi-tile engravings that could recount long years of industry and achievement.
So, needing one iconic image, that's what they engrave: Births, deaths, creation, destruction, individuals. In most fortresses there WILL be plenty of engravings of the splendor of the fortress, but they'll all be more specific than just that. Look for engravings of your founding, or the rise of kings to the throne of your civilization, the appointment of your expedition leader or baron, the forging of artifacts and the creation of masterworks. These are the displays of your wealth and power, your glory and your achievements. It just so happens it's ALSO easy to engrave deaths of countless goblins, dwarves at their hands, or random historical maulings.
Where does all the water go when channeled through fortifications off the edge of the map, 50 z-levels underground in otherwise solid rock?
It drains into an aquifer. No aquifer nearby? that's okay, it'll get there.
EDIT: I'm supposed to ask a question...
Why do goblins keep coming when none have ever left my fortress alive?