A different style game has a rather huge, game changing mod. I've been using it for about a week and it greatly improves the game. It has tons of features, along with a custom tileset. Its based off of Dwarf Fortress, but adds lots. The graphics are just...well...tilesets...but I like it a lot better than ascii (hard to know what is going on for me, with ascii)
It is Masterwork DF2. Even adds hotkeys and what not, and can make it easy/hard as you want (lots of options to tweak the mod settings to what fits you). New races, buildings, allies...it adds tons of features. The mod page pretty much sums it up in a short read.
http://www.bay12forums.com/smf/index.php?topic=98196.0