Some of the pictures:
[spoiler]
[Image: http://sphotos.xx.fbcdn.net/hphotos-ash3/s720x720/525960_375966035802324_1707658273_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-prn1/s720x720/539749_375966302468964_375885161_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-snc6/s720x720/198345_375966085802319_355383729_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-snc6/s720x720/252791_375965719135689_776597386_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-ash3/s720x720/563365_375966142468980_1915339469_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-snc6/s720x720/282393_375965839135677_1947033195_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-ash3/s720x720/557241_375965909135670_340070331_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-ash3/s720x720/544967_375966239135637_1008278225_n.jpg]
[Image: http://sphotos.xx.fbcdn.net/hphotos-snc7/s720x720/380704_375966289135632_719512461_n.jpg]
[/spoiler]Xen...?
If you require confirmation: http://forums.steampowered.com/forums/showpost.php?p=31360460&postcount=89
We wouldn't post anything unless it was 100% confirmed. Sometimes we post things with a question mark at the end. This isn't one of them. This is official (albeit old) Valve concept art for Episode 3.