The file xdoom.wad is a PWAD file which gets automatically loaded by XDoom,
from directories /usr/local/games/xdoom or $DOOMWADDIR, in this order.
This PWAD file includes new lumps for XDoom, like the translucency table
and new sound for the chaingun. The pre-compiled xdoom.wad just is build
how I like things looking and sounding, feel free to play with it and adjust
it to what you like. All raw data to rebuild xdoom.wad is provided here, but
please note that you need xwadtools from ftp://ftp.cdrom.com/pub/doom/source
to build xdoom.wad your self. Xwadtools includes all and any tools to
manipulate WAD files, I have working under UNIX. To rebuild xdoom.wad simply
type make in this directory (after you installed xwadtools, that is),
'make clean' to remove the temporary files generated.

The files in this directory are as follows:

xdoom.res:	This is the response file used for 'mkwad' to tell, which
		non graphical resources to include into xdoom.wad.

xdoom.wgc:	Input file for 'wadgc' used for the graphical resources
		in xdoom.wad.

swantbls.dat:	Input file for 'swantbls' with the default switches and
		animated textures/flats in the id IWAD's.

watermap.dat:	Underwater colormap extracted from Boom resource WAD.

dschgun.sfx:	This is a weapon sound I took out of Marines Doom, the included
		text file doesn't limit usage of the PWAD in any way. With this
		the chaingun now sounds like a big bad weapon and not like a
		rapid firing pistol anymore. If a PWAD file includes a lump
		DSCHGUN it will be used for the chaingun without an impact on
		the pistol sound. If the lump wasn't found, XDoom will default
		back to the pistol sound, like original Doom. So if you liked
		the original Doom chaingun sound just take the lump out of
		xdoom.res and rebuild xdoom.wad without or use XDoom with
		option -nochgun.

m_cdvol.ppm:	Image file in PPM P6 format, this image shows the text
		'CD Volume', used in the sound setup menu.

m_horsen.ppm	Image in PPM P6 format, shows menu text 'Horizonal' for
		horizontal mouse sensitivity setting. This image was taken
		from the Boom resource WAD.

m_versen.ppm	As above, for vertical mouse sensitivity, from Boom too.

comdev.ppm:	XDoom allows communication with a handheld computer gadget.
		This is the image for the device.

dsbeep[n].sfx:	Sound alerts for the gadget. Sounds were taken from a PD
		CD-ROM with sound effects. Files were in wave format,
		converted with sox into 8bit 11kHz raw format and then
		converted with raw2sfx (included in xwadtools) to id's sfx
		format. Link the one you like best to dsbeep.sfx to be
		included in xdoom.wad.

common.acs:	The system include files for acc for XDoomPlus. Do NOT
defs.acs:	use the includes that come with acc, they are for Hexen
specials.acs:	and XDoomPlus is not Hexen! This files should be copied
		to /usr/local/lib/acc/xdoom, the top level makefile does
		this for you.

wvars.acs:	Example include file for world variables. This file must
		be provided in a PWAD directory using scripts, because
		common.acs includes it from the current directory.

The file multigen.txt is the input state table for the tool 'multigen',
which compiles info.c and info.h for the game engine from this state tables.
The state table is modified to render several sprites translucent and to
add a smoke trail to player and Cyberdemon missiles. The original, unmodified
version of this file from id Software is included in xwadtools in the multigen
source directory.
So if you don't like some of the modifications I did, just get xwadtools
and compile info.c and info.h from the original file, or change things
to your liking anyway, whatever.
To get rid of translucency remove the MF_TRANSLUC flag from the thing flags.
To get rid of missile smoke trails change the action function for S_ROCKET
from A_Tracer to NULL. Then compile info.c and info.h from the modified state
tables with multigen and replace the ones in the xdoom source directory with
your new ones and recompile the game engine.
