I'm looking into changing out the rear seat for one with a movable headrest. I don't want the carseat leaving a mark on the headrest. Does anyone know anyway to not have a mark left on the headrest?

What kind of car seat? I have not had any problem with the Evenflo Titan in my Limited, which is a short seat. The next seat for my older child is a Birtax Regent that is actually taller than the headrest! She'll be in that within a month as my younger moves up to a cenvertible.

I have these car seat protectors (http://www.target.com/Eddie-Bauer-Car-Seat-Protector/dp/B000COW82C) for every car seat since all my vehicles have leather.

I'm not worried so much about the bottom I have that covered. I have an Graco that I mainly use. I do want a Britax but they are expensive. The Graco is about 4-5 inches shorter than the headrest. Is there a solution so the headrest doesn't get reshaped/wrinkled?

I have the Gracos as well. Recline the rear seat back so that it doesn't bind against the headrest so hard. I found the kids are more comfortable that way as well.

But does the carseat still fit against the back of the seat? Is it safe to do that?

It is safe, as long as the seat is secure. If you are concerned, you can always fold a washcloth or small towell to put there before reefing on the belts.

Hmm I'll have to check it out tomorrow. Thank you for the advice!!