My "new" Marlin 45-70 Cowboy was just crying out for a leather butt cover, so I made one last night and stained it today.
1. Raise the comb a little, to allow scope use but without compromising irons
2. Increase length of pull (the gun is a little short for me)
3. Soak up recoil
4. Hold some ammunition
5. Protect stock
6. Not look totally gash
It's veg-tanned leather which I've stained with Fiebing's "Antique leather finish", followed by a Carnuaba wax mixture then polished.
I'm no leatherworker but I think it fulfills the goals set (can't comment on recoil yet.)