How much graphics can I legally use?

So, I'm working on a project that is very much themed Rhett&Link. Now, for the time being, it's a secret, (hopefully just a few weeks it'll go public) but I need to know, how much of your graphics and stuff can I use legally? 

Like, clips from songs, logos and graphics you guys made/own, stuff like that. 

Any help would be great! I asked in the chat, but nobody really could answer. So, maybe Rhett&Link could answer? But really, anybody. :)