After literally fives of minutes of exhaustive research I was unable to find an ASCII tileset that looked comfortable on an HD monitor, so I made my own. This tileset is the default ASCII, with each tile redrawn by hand and some very light shading done. It runs natively in 1280x500, which I found to be the best compromise between the aesthetics of square sets and the compact efficiency of default ASCII.
This is the final version I'll be doing. I managed to round off the wall corners fairly nicely, as well as some tiny things here and there.
Screenshots:
(https://dl.dropbox.com/u/62441899/Shizzle%20tileset%20screenshot.PNG)
(https://dl.dropbox.com/u/62441899/Shizzle%20tileset%20screenshot%202.PNG)
(https://dl.dropbox.com/u/62441899/Shizzle%20tileset%20screenshot%203.PNG)
DFFD Download: http://dffd.wimbli.com/file.php?id=7205
The ZIP is designed for use with Lazy Newb Pack, just unzip into your LNP/Graphics folder.
Just the source image:
(https://dl.dropbox.com/u/62441899/shizzle_1280x500.png)