I have just released some stuff to aid in creating/editing virtual keyboard layouts on the N900, including layouts for the "special characters view" (i.e. what you get if you press "sym")
Download http://www.cncmods.net/files/vkb.zip
The following files are included:
decode_vkb.pl script to decode a .vkb file to XML for editing (its a modification of an existing Perl script, it now properly decodes everything the N900 vkb parser will parse)
gen_vkb binary for program to generate a .vkb file from an XML file (its a clone of the gen_vkb from older Maemo versions but it supports all the N900 features)
gen_vkb.c source for gen_vkb
gen_vkb.sh script to compile gen_vkb.c
imlayout_vkb.h header file you can use to talk to the libimlayout library (which loads and parses the vkb files)
vkb-format-v4.txt (modified/updated description of the .vkb file format)

If you wish to compile gen_vkb.c, you will need to put gen_vkb.c and gen_vkb.sh in a folder on your scratchbox setup, then put imlayout_vkb.h in your /usr/include, then make sure you have the libimlayout0 package installed in your scratchbox install, then create a symbolic link from /usr/lib/libimlayout.so.0 to /usr/lib/libimlayout.so. Then run gen_vkb.sh.

gen_vkb should compile and run for both x86 and ARM if you have a usable libimlayout library available.

The stock vkb files are in /usr/share/keyboards and /usr/share/scv_layouts