I am trying to make my small open-source non-commercial web project for training purpose and put it on GitHub for Version Control purpose. It is a non-commercial product, just to show my friends. And to get to know with web programming.
However I am not a graphic, and I wanted to use some 3d modeled portraits provided with CEP, or some item images.
I do not know the licence of this project, and as I will not take any benefits from my project I wanted to know If I could use some of them.
Of course I will share my project if you want 
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While I don’t speak for the CEP or 99.999999% of the content in it (@TheAmethystDragon is the CEP’s current curator (::wink wink, nudge nudge, convenient “somebody mentioned you in a thread”-alert::)), I’m quite sure you can do that without having to worry for an instant. NWN’s got a very laid-back open-source-loving community in general.
Licensing-wise, the CEP incorporates work from many different authors. It’s not impossible that someday an original author of a particular piece of content will come and complain to you a la “Hey! I allowed the CEP folks to use my content, who the heck are you?!”, but it’s very unlikely. Most of the people who’ve contributed to the CEP were already well-disposed towards strangers using their work for fun and learning. As long as you don’t try to make money off somebody else’s work and, whenever possible, credit the original sources, you’ll be fine, and probably get reactions more along the lines of “Yay! My work is being used! The time I have put into creating this has not been wasted!”.
If you want to stick to the rules strictly, the “Open - Free & open only if project also open” restriction on the CEP means that you can use it, but you’re not allowed to place tighter use restrictions on your derivative in turn. The absence of “Redistribute as is”, “Redistribute with corrections/modifications”, and “Allow Distribution in others work” flags means you shouldn’t start redistributing the CEP itself.
It’s all kind of a gray area, anyway. “Try not to be a jerk” and “When in doubt, talk to people” are the best guidelines to follow, but you’ve already got those down pat just for thinking to ask this question. Worst case scenario, someday somebody comes and asks you to stop using a particular piece of content, and you’ll have to dig it out and replace it with something else.
Looking forward to your project! Come shout if you run into problems (and googling doesn’t help). 
The Vault guidelines concur, as long as you observe the Permissions & Licensing on the CEP download page by keeping your work open.