I have prepared a script for building such blocks and present it to you here; all you need is to select a text and voila, it stands out on Document Map now.
I have picked one font from Text to ASCII Art Generator (TAAG) and modified it a bit, but you may pick another (and build up it's definitions), if you want to
I could tweak my script to allow easier defining of letters, but first I need to get PosForm() working. FYI I tested Banner3 (7 chars high), but decided it was too big (and hence the headers were too short.)You can switch "building block" (i.e. ASCII character) for your header, if you prefer it to be darker or lighter than default one (#); I have given some suggestions in the script.
Length of your header depends, of course, on your Document Map's font size; with font at 5 points you can see up to 7 letters, with 4 points up to 10 and with 3 points (that's my assumption, because it serves me well) up to 14.
Enjoy!
