I've been asked to do a birthday cake for a 60 year old history buff who is religious. Any suggestions/ideas - can be either history or religious theme. I'm drawing a total blank.

AND, he is also on the brink of major heart surgery.

I'd stay away from the heart surgery for sure.
Not even sure I'd use the history info but make it rather simple w/a cross and maybe even some flowers but in blues & greens; maybe tan &/or brown worked in.

How about a type of "time line"? Choose a few important historical events with, of course, his birth 60 yrs ago. Then, depending on his faith, you could add an historical event for that.

wow, that's a good one, you can do the parting of the sea, moses/10 commandments and tie it in with an actual historical fact from his hometown or country depicted on top of a bible, good luck, many ways to go with this one

Well, Moses was 80 yrs old when he crossed the Red Sea,and Abraham was 100 and Sarah was 90 when she gave birth to Isaac, maybe something reminding him that age has nothing to do with greatness.

I immediately pictured a bible, possibly open to a particular passage. Maybe a bookmark with something special from his life depicted on it.

The attached is what I ended up doing. Using the frozen buttercream transfer technique. It was much more detail than I normally do but they loved it. I love using this technique (I tire of flowers!) but I'm always a bit nervous until I get it on the cake so I can actually see how it turned out. I allow plenty of time in case I need to redo it or go to plan B.