Hi,
due to the lack of large square tilesets, I created my own 24x24 antialiased translucent tileset

.
It is based on the Terminus24 24x32 tileset. However, I have redrawn almost all tiles, and designed the square font from scratch...
The tileset tries to preserve as much of the original ASCII tileset feeling as possible, so not too many "graphical" symbols to be found in there

It is available here:
http://df.magmawiki.com/index.php/Tileset_repository#Bisasam(Requires DF 40d16+ due to transparency. When the merge is completed, it should also work with 0.31.x)

Screenshots:
There is also a 16x16 version available here:
http://df.magmawiki.com/index.php/Tileset_repository#Bisasam_2
Screenshots:
Update:I've made a 20x20 version:
http://df.magmawiki.com/index.php/Tileset_repository#BisasamIt comes in two flavors; first the graphical one (like the 24x24 and 16x16 versions):

And, second, a new ASCII version which replaces the graphical tiles by ASCII ones:

I'm using the following color theme (init.txt):
[BLACK_R:0]
[BLACK_G:0]
[BLACK_B:0]
[BLUE_R:73]
[BLUE_G:95]
[BLUE_B:157]
[GREEN_R:89]
[GREEN_G:117]
[GREEN_B:55]
[CYAN_R:101]
[CYAN_G:144]
[CYAN_B:158]
[RED_R:146]
[RED_G:0]
[RED_B:0]
[MAGENTA_R:165]
[MAGENTA_G:54]
[MAGENTA_B:101]
[BROWN_R:138]
[BROWN_G:105]
[BROWN_B:59]
[LGRAY_R:128]
[LGRAY_G:128]
[LGRAY_B:128]
[DGRAY_R:80]
[DGRAY_G:80]
[DGRAY_B:80]
[LBLUE_R:111]
[LBLUE_G:138]
[LBLUE_B:165]
[LGREEN_R:160]
[LGREEN_G:200]
[LGREEN_B:82]
[LCYAN_R:159]
[LCYAN_G:196]
[LCYAN_B:210]
[LRED_R:206]
[LRED_G:73]
[LRED_B:1]
[LMAGENTA_R:239]
[LMAGENTA_G:150]
[LMAGENTA_B:207]
[YELLOW_R:255]
[YELLOW_G:198]
[YELLOW_B:0]
[WHITE_R:255]
[WHITE_G:255]
[WHITE_B:255]
So try it out, and discuss
