Okay, I went and looked up what keyboards are actually being used on various Zeppelin songs. How 'bout these -- definitely rock songs:
Acoustic Piano
"Friends"
"Boogie with Stu"
"Rock and Roll"
"Hot Dog"
"The Rain Song"
"Southbound Saurez"
"Darlene"
Electric Piano
"Misty Mountain Hop"
"No Quarter"
Organ (Various, but usually an acoustic-electric hybrid)
"You Shook Me"
"Your Time Is Gonna Come"
"Thank You"
"Since I Been Loving You"
"Night Flight"
"Dancing Days"
Other Keyboards
Clavinet (stringed keyboard), "Trampled Under Foot"
Clavinet, "Custard Pie"
Clavinet, "Into the Light"
Mellotron (doing recorders), "Stairway to Heaven"
Mellotron (doing strings), "The Rain Song"
Mellotron (doing strings), "Kashmir"
Synth Keyboard, "All My Love"
Synth Keyboard, "Carouselambra"
Synth Keyboard, "In the Evening"
Synth Keyboard, "I'm Gonna Crawl"
You might not care at all about this if you're only interested in the clear sound of an acoustic piano. But I tend to think that all keyboard instruments have a similar effect, if not sound, because of the way they're played. And if you're looking for rock songs with only acoustic piano, well, good luck -- it's pretty tough to get a piano to sound good on a rock stage, which is why a lot of bands use other keyboards.
kerely
[Edit: And sorry for completely missing the 'new' in the thread title.]