So I replaced the strings on my Ibanez SDGR bass for the first time last night and now every time I play the low E string there's a noise coming from the headstock area. It kind of sounds like something is loose up there. I generally only hear it if I'm playing with my fingers. If I use a pick and downstroke the string it usually doesn't make this sound.

Any ideas?
Did you lower the string gauge? It might be loose in the nut and rattling. Otherwise try to hold stuff while your playing to make it stop, most of the time it's something with the tuning pegs. Usually not a big deal unless they are falling out...
It could happen if he went to a higher string gauge as well, and the string jumps out a little because it doesn't have a good seat.
I think it might be the gears in the tuners.

I have no idea what gauge my stock strings were but the string seems to sit well in the nut.