My grandfather was buried with a special pillow to rest his feet on. All the grandchildrens names were put on the pillow. Wonderful gesture to rest his 'aching feet' from a long life and the illness that eventually took him.
I have seen the pillows you are talking about on caskets. The ones I have seen are quite small, with a larger array of flowers as you have in your picture. The whole pillow/flower arrangement is not very big, as there is usually a much larger floral arrangement sitting on top of the bottom half of the casket also, which is then moved to the center once the casket has been closed.