- Kiss the Cross: Old Ethiopian Orthodox tradition dictates that all priests must carry their Crosses prominently. Any of the faithful who encounter a Priest kiss his Cross for good luck. The Priest is expected to touch any stranger he meets with his Cross to bless them. Apply that concept to your next D&D Cleric for some very cool role-playing opportunities. "I walk into the tavern, and make the customary rounds of touching every patron with Pelor's Sunsign." If someone resists, it might mean they're a vampire, or just a follower of a competing God.
- St George Church in Lalibela, Ethiopia is a work of awe-inspiring architecture. It's a church in a pit, the whole church literally carved out of a single rock. I could picture a world where every Church of Moradin were built the same way - or maybe every Dwarf settlement. Entire castles built this way might be practical in a setting with Move Earth spells, provided more aerial threats exist than burrowing threats in the game world.
- Red Ink is the Word of God. The exhibit featured old hand-copied Bibles and Korans. In most of them, everything that was the word of God was in red ink - descriptions, narratives, and dialog from other characters was in black. The fantasy gaming interpretations of this are pretty cool. Just as in certain kingdoms only royalty could wear purple, you could have a fantasy priesthood claim a monopoly on a certain color of ink. "Only the words of Correlon may be written in Cyan, you Heathen!" Or perhaps spellbooks / scrolls could require certain colors of ink to function, and so seeing a particular color of writing was a tip off that it was magical in nature. Some Magical Order might have convinced the King into granting them a monopoly on a color, and without access to the orange ink, no other wizards can pass on the secrets of Transmutation spells.
Feel free to use those ideas in your campaigns - they aren't mine, they belong to Ethiopia. :)
P.S.: Go to the Lucy/Ethiopia exhibit at the Pacific Science Center if you live in Seattle. It's chock full of cool information.