http://creativecommons.org/licenses/by-nc-nd/3.0/gr/

Quote from that page:
"to Share — to copy, distribute and transmit the work"

It doesn't say "to use in your mod". Also, using others stuff to build a mod means build that mod upon others work. You don't just have a pack of various skins and redistribute them all together. That is totally ok because that is distribution but here is different.

Still I admit that it's a bit vague. It would be nice of yours though to pm or e-mail the authors or submitters of the things you are using just to be sure.

Also my bad about Valve's content. Those screenshots tricked me. :P

Finally, some feedback for your mod.
Upgrading the graphics of CS:S is a good concept. Using another engine to do that, is a bad idea especially if that other engine is Crytek. Your mod will be played only by the ones who have or can afford a powerful enough system to run Crysis.

There's a studio here on FPSB working on a mod for CS:S as well. The mod's called CS AfterSource. It includes upgraded models, skins and maps which use all the latest technologies of the Source engine, thus upgrading it visually but preserving some good performance even on medium end systems.

Yours is not really an upgrade but rather a rip-off on another engine. That's why I would suggest to include new gameplay features, more balanced weaponry and maybe some more playable characters like the ones seen in CS CZ.

I'm not saying it can't work as a mod. I think it will but it surely needs something to spice it up.

It would also be a good idea to change the screenshots in the mod's page here on FPSB. :P

I would post this in the Counter-Crysis page but since FPSB is bugged it seems that I can't so I'm posting this here.

You can only redistribute work. You cannot build upon it. Having somebody's work in your mod without his permission means building your mod upon others work.

Redistributing means keeping the rar or zip file intact and uploading it someplace else by giving credit to the original author.

Also, porting stuff from Valve games to Crysis is illegal.

You can only use anything from Valve games in case you are making a mod on the Source engine with the Source SDK.

Please read Valve's EULA here.

Your mod is currently illegal.

Yaw where the hell do i join the studio? :S

Yew arr a poirat. Yarr.

Why the hell do you insist so much? Does it bother you? Oh wait you probably hate me and have nothing else to do, and as you were given Moderation on fpsbanana you feel it's your responsibility to ruin peoples day with pointless things, why wont you just go bother somebody else posting content that actually infringe copyright laws in fpsbanana