What proof beyond the Bible is there that Jesus existed?

Besides The Bible there has been a finding of a piece of the cross he was crucified on but the main answer to this question is you have to have FAITH. If you truly believe you can begin to understand the message behind the crucifixion of Jesus.

Answer/

There is The Acts of Pilate found in research by Ananias , an officer of the Praetorian Guard, who translated into Greek the report recorded in Hebrew by Nicodemus of the Passion of Jesus Christ, A.D.33.

There are also the reports of Pilate sent to Tiberius concerning the crucifixion. Ref: The Letter of Pilate to Tiberius; Anaphora Pilati.

Primary sources are documented within these editions:

S. P Brock, A Fragment of the Acta Pilati in Christian Palestinian Aramaic; J.W.B. Barns, Bodleian Fragments of a Sahidic Version of the Acta Pilati,' in Coptic; I. E. Rahmani, Acta Pilati: Antiqua Versio in Syriac, etc.