Here’s something you don’t see every day — a 1298 Eastern Orthodox fresco from the Church of St. Nicholas in Prilep, Macedonia, showing Jesus voluntarily climbing onto the cross. And yes, he is climbing up, not down, as we can see from the Greek title inscription:

Here it is:
Ι[ησού]ς Χ[ριστό]ς ἀναβενωντός ἐν το σταυρο (standard spelling ἀναβαίνοντός ἐν τῷ σταυρῶ)
Iesous Khristos anabenontos en to stauro/anabainontos en to stauro
The verb here is ἀναβαίνω anabaíno, meaning “to ascend, to go up, to climb.” So we can translate as:
“Jesus Christ Ascending the Cross,” or more colloquially as “Jesus Christ Climbing Up Onto the Cross.”
Now if you are familiar with the New Testament accounts of the Crucifixion, you will know there is nothing at all in them about Jesus climbing a ladder onto his cross. It is a theme that developed outside the Bible, and one that seems to have been restricted to a certain period in its popularity.
Now remember that the island of Crete became a possession of Venice (Italy) in 1204-1205, and we know that Italian influence on icon painting only increased through the appearance of the Cretan School from the 15th to the 17th century. But the Macedonian fresco dates to near the beginning of the 1300s, much earlier than the Cretan School. Yet as I often say, there was never a “pure” Eastern Orthodox iconography untouched by outside influences.
Let’s look at a Crucifixion with associated scenes attributed to the Italian Florentine painter Coppo di Marcovaldo (1225–1276):

Such medieval Italian crucifixes always remind me of St. Francis of Assisi, who died in 1226. Probably too many viewings of the movie Brother Sun, Sister Moon.
If we look at the bottom scene on the left side, we can see a relation with the fresco:
There Jesus is, standing with one foot on the lowest rung of the ladder, as though getting ready to climb up it.
We can jump to about 1300-1320 to look at an Italian miniature by Pacino di Buonaguida/Bonaguida:
There we see Jesus climbing resolutely up onto his cross, though by modern standards of perspective, the ladder is at an angle that would cause a nasty fall.
We can move on to the image likely painted about 1270-1280 by Guido da Siena — much more reminiscent of the Macedonian fresco:

I do not know just how the iconography of Jesus ascending the Ladder got to Macedonia, but it certainly appears that it was due to Italian influence and the appearance in the 13th – early 14th century of this apparently then new visual representation. How and why did it begin? We are not certain of that either, and as we see in the example by Guido da Siena, Jesus was not always shown ascending the ladder entirely voluntarily; notice the man atop the crossbeam reaching down to grasp the left hand of Jesus and pull him up:
There are, of course, speculations as to the possible origins of the rather uncommon depiction of Jesus climbing the ladder onto the cross, and if you would like to begin exploring that topic, you might like to read this paper, though it has really nothing to say about the presence of this iconography in a Macedonian church fresco from the end of the 1200s. It is by Anna Anna Eörsi, and titled “Haec scala significat ascensum virtutum. Remarks on the iconography of Christ Mounting the Cross on a Ladder.
http://arthist.elte.hu/Tanarok/EorsiA/Fulltexts/Idegen/l%E9tra_a.htm
I had barely posted this article when I received a comment from a clever reader in the Netherlands, mentioning the very relevant “Dream of the Rood” (Rood means cross here), an Old English poem in which the cross speaks these lines about the Crucifixion:
“Then saw I mankind’s Lord
Hasten with great zeal, as though he wanted to climb on me.”
(Geseah ic þā Frēan mancynnes
efstan elne micle, þæt hē mē wolde on gestīgan.)