Teh Galil!

[Victor]

Their licence is actually pretty good:

Code:

You are permitted to use our textures to design as many projects as necessary, including those you are creating for your clients. You may not resell or redistribute the textures in any other way, modified, unmodified, standalone or combined with another product without prior written (email) consent from us.
...
You may not claim intellectual or exclusive ownership of any of our texture photos, modified or unmodified. All texture photos remain our property.
None of the textures or a derivative of the textures may be copyrighted. If you have a question about the legal use of any of these textures please email us and ask us about it.

So you can do whatever you want as long as it's part of a project, but the project must not be copyrighted. You don't even have to provide credits to them, as long as you say that the textures came from a "source that does not require attribution, but requires that the textures be non-copyrighted". But it's easier just to link to their site.