In Oblivion there wasn't really much I could take as a trophy, so at later levels I would simply strip the body of all armour and either sell it, or add it to a collection.
I did this In Oblivion aswell. About halfway through the main quest money was no longer a problem and since then (about 100 hours ago gameplay) I have kept everything picked up/looted organized in containers in Rosewood in Skingrad. My weapons chest only gets to the Glass weapons because apparently it won't load the entire list, same for armor, potions/scrolls etc.
I am big on collecting in the open world games. And adding a skull pile from my kills would add a huge amount to it. I would try and build monumental piles of them, each organized by skull.