no glass, my bad!

isn't a decal basically a texture with alpha channel, but hard alpha (black and white, no gray or only a little bit)?

impact marks are decals as well, they need an extra sort setting. The kind of decals you talk about don't i think... I believe the reason why the impact marks show on stock textures is, that there's a solid texture (DXT1, no alpha) underneath as 'base' to receive impacts.

if you got photoshop, you should have a look at the stock files. you can use Regolith's IWI_X_DDS converter: http://diegologic.net/CoD/iwi_x_dds.htm

The important steps are explained here:
http://wiki.modsrepository.com/index.php/Call_of_Duty_4:_Textures
The channels are changed, so you need to edit the dds-output a bit.

GIMP might also work, but i'm not familiar with it so i can't test for you.

Maybe there's a problem with the cloth surface type. Try changing it to something else (something similar) and see what happens.

Also, you said that decals work if blendFunc is Add.
Then use these settings:
blendFunc: Add
alphaTest: Always
depthTest: GreaterEqual

If it doesn't work, try the other settings for alphaTest.

I'm getting crazy with this alpha texture. I opened "egypt_cloth_bed" which is a texture with an alpha channel and is a type carpet with surface type cloth with Photoshop (after exporting it with the tool Sevenz gave me) and it is same built as my texture.

I tested all what you said cskiller, and it doesn't work. It's like there wouldn't be collision, because the bullet mark is shown behind the texture (I moved it a bit up and the mark is shown at the ground).

Could somebody help me with that please?

is the patch or brush surface with your decal assigned on perfectly aligned with the underlaying surface? (same plane, exactly in the same depth)

Okay, I came to the next conlcusion:

My carpet:
- If you shoot at the black part of the alpha channel, the bullet marks are shown on the texture and below (on the ground), see first attached file.
- If I try to use it as a decal (placing the texture exactly in the ground) it doesn't work well, see second attached file.

Game carpet (egypt_cloth_bed):
- If you shoot at it, the bullet mark is shown always on the ground (behind the texture) AND you see the mark through the texture so it seems to be on it .
- You can't find the texture under the "decal" locale folder on Radiant, but it seems to work as one.
(for both points look at the last attached file.)

So, what to do now? The wierd thing is the thing with the egypt_cloth_bed. It is under the "locale: cloth" in Radiant, but not under "decals".

For the flickering problem, you have to change the sort from default to decal top level 3 (or something like that). Although, that was the setting in CoD4 Asset manager, not sure if it's the same in CoD2.
That will eliminate z-fighting (flickering).