The Trinity with Christ as a Child
MURILLO, Bartolomé Esteban
The word "Trinity" does not appear in the Bible. The idea behind the word is definitely biblical, though. The Trinity is, of course, the God of both testaments. The physical appearances of God in the NT (e.g. Jesus Christ, the Holy Spirit as a dove) is focused in the artwork dealing with the Trinity.
Heavenly and earthly trinities, The (C. 1675-82):
Angels in upper right corner