There are two types of church quotes that are popular: quotes from famous theologians about church (or other topics) and Biblical quotations, which churches often use and display.
For example, C.S. Lewis, Martin Luther and John Calvin are well-known and influential theologians. They are often quoted by clergy and church members. Also, there are several well-known verses and scripture passages that Christians use to encourage one another. John 3:16 is a popular verse that is often quoted and displayed in churches and Christian homes. A popular passage like 1 Corinthians 13 may also be quoted in whole or in part in churches as well.