Default Downloading Mods for ROM

I apologize if this is in the wrong place.

I've decided to follow some simple tutorials on creating a custom ROM. It seems that you can add your own mods to your ROM, but I have no idea where to download any. I've done searches and I'm not finding anything. Can anyone point me in the right direction?

Also, I did find one mod which is called 'Awesome Beats' which is a Beats by Dre mod, but it's posted under the LG Optimus phone. Does that mean I can't download that particular mod and add it to my ROM?

Thanks in advance.