Please put the files where they should go inside the installation as is explained in the Packaging Guide - meaning "data/chars_frosty_glassy.png"; also you should really provide a CFG file with your font-image .. should make life easier for you too - I guess it was quite a hassle to put all the chars where they are inside the original image, with a proper cfg you're more flexible!
Also mention prominently that this approach should be put into the personal-home-dir or it would require people to overwrite the vanilla CFG file "data/font.cfg", which they really shouldn't do.
BTW: all you need is the TTF-2-Font tool by quin. Take your favourite TTF font and let it provide you with a CFG, it should actually be ready to use for sauerbraten as-is, or at least with only a few minor tweaks.