Add-Ons
Are Third Party Campaign (Made by the community), that will allow content authors to package their maps, movie posters, models, and textures into a single .VLK file. Installation of these add-ons are a simple double click to download and install.
If preferred you can download and then drag the file into the add-ons folder that will be added to your steam client in the next update. The Add-Ons option will be selected from the Extra’s menu on the Menu Main (See Below).

For the full first look head on over to Absolute Left 4 Dead
June 22nd, 2009 at 10:57 pm
nice to see that valve will give a lot more power to the people for variety, I’ve tried custom maps and its a pain to set up and use. Hopefully the add-ons feature will work with skins too as you have to alter your own .VPK which just sounds like a bad idea.
P.S.It’s .VPK not VLK