Like many other venues, there are explicitly Christian organizations devoted to psychology; the American Association of Christian Counselors is probably the largest. Here is an interesting article: The Psychology of Religion; it's more of an analysis but contains a lot of good information.
Thomas Aquinas is noted as having a significant place in the history of the development of psychological thought. Later, Puritans and Pietists, like John Wesley and Jonathan Edwards contributed to psychological thought by their contributions to pastoral counseling and spiritual development.
PS: Jung was not a Christian. He abandoned his father's faith in his early teens.
The survey linked below, which is fairly comprehensive, mentions astonishingly few major modern psychologists who strongly identified themselves as Christians. James McCosh of Princeton University is one, but apparently many major psychologists in the late nineteenth and early twentieth centuries were unfriendly toward Christianity or saw it merely as an object of study. Many of these people even psychology as a kind of replacement for Christianity. This might help explain why such convinced Christians as Flannery O'Connor were often hostile, in turn, toward psychology. O'Connor often mentions Freudianism and Jungianism as if they were in competition with Christianity.
I agree with answers about Jung and Lewis.
I know the distinction between believing in God and being a Christian. Though "messianic complex" is not listed in the DSM (listing psychological disorders), Alfred Jones, at the turn of the 20th Century was a psycholanalyst, was familiar with Freud's work, and was the first person to refer to "God complex" (also not listed in the DSM). I cannot say for certain if he also coined the phrase regarding the "messianic complex." I'm not sure if this counts or if it helps.
C.S. Lewis wouldn't consider himself a psychologist, but I would submit that his writings have influenced a great many people to become more aware of how the Christian faith shapes their lives and attitudes. He presents powerful examples of faith in his written work.
There were many Christians that had a great influence in all areas of society, even psychology. Let me name a few of them. Friedrich Daniel Ernst Schleiermacher was one of the greatest theologians of the 19th century and he influenced a generation of scholars, which also had a influence on psychology. I would also say that someone like Martin Luther King Jr. had a great influence in the area of non-violence and the importance of equality.
Was not Carl Jung a Christian? He definitely had an extensive Christian background and his theories and ideas about psychology have been used and incorporated into mainstream religious belief in many denominations. He was certainly a massively influential psychologist whose ideas were shaped in part by his Christian upbringing.