Someone could post a scripture and the next person would have to look it up and post what scripture it is.
Or someone pick a name, place or event from the Bible and the next person would have to come up with another word with the last letter of the posted word. For Instance: JOHN, then NICODEMUS, SAMARITAN, NOAH, etc....
Or someone could post a book and a keyword from that book of the Bible and another person would have to guess the chapter and verse and then write the verse. But you would also have to tell that person which Bible you are using, NKJ, NIV,New Living Translation, etc...
For instance I am thinking of the Book of John and my keyword is begotten from the NKJV. Then another person would probably guess John 3:16 "For God so loved the World that He gave his only begotten Son....
Well, there are three ideas. Pick one or come up with one of your own and run with it