Every now and then some poor, misguided soul will complain that square tilesets are hard to read, usually deluding themselves into thinking that rectangular tilesets are somehow superior. (I'm actually just trying to be funny though, no flaming intended!)
Anyway, IMO the problem usually isn't that the tileset is square, the problem is that the font used is often too small for the tile size it's used in. The kerning is often off. If your square tileset uses a properly sized font, the readability problems mostly go away. I've realized for a long time now that my fonts are too small for 10x10, which affects readability. I didn't mind as much before because the extra black space reminded me of Ultima V (most of my childhood gaming), but it's really been wearing on me now that I obsessively read over and improve creature descriptons for Revised.
So farewell, 10x10 (and 20x20, by extension).
So 8x8 is probably too small, so I'm giving 9x9 a shot. Consider this a preview. I was planning on doing everything in one fell swoop and surprising people, but between Revised taking up a lot of my attention and various IRL problems that complicate my ability to work on DF I thought I'd post something now. This also lets me collect feedback. Tasty feedback.
9x9 Taffer? What?
And blocky 18x18, of course.
Old and busted (and hard to read).
New hotness (and much nicer to read).
Maybe the walls are too fancy?
I took the opportunity to make water/snow/sand less noticable while I was at it. This is much better after all, and helps to alleviate the worst part about diagonal walls (empty black corners in snowy/sandy areas).
Enjoy! I don't have a release date. I'm not even completely sure I want 9x9 and not 8x8. 8x8 is even more pleasant to read, but then niceties such as accented characters and the fancier tiles start suffering. I'll also be wanting to fix up Damascus's readability problems while I'm working on this, and I haven't even started any of the fonts but this one. What can't be adapted will be dropped, but I expect all of the fonts to survive (even Damascus). I also don't know yet what this does to the creature graphics. I'll probably need to redraw them all. I'm seriously tempted to just stick to the "dwarves as letters", because I'm getting older and crankier and I haven't actually used my creature graphics for years (seriously).