As an alternative to the Creeper Shrine here is a heavily weathered Creeper Skull with 8x8x8 dimensions. Also in comparison to the Creeper Shrine here better outdoors.
Because of the 8x8x8 dimensions the proportions look much better. Besides Cobblestone in all variations and Stonebricks in all variations, I used Andersite (normal and polished).
The interior of the skull is initially a maximum of 4×4, but since I had a larger footprint in some places further down (due to severe weathering), I was even able to build a small mushroom farm inside with fully automated harvesting.
EDIT: Now with video of the finishing touches!