I don't ever remember seen palm leaves used as token of
victory. I have seen "laurel" so used many times.

The Victor's Laurel Wreath.

In the Greek athletic games, a laurel wreath (Stephanos in Greek), or crown was given to the winner. In itself it was worth nothing, but it was a great honour to win and wear it. In mockery, the Romans gave Jesus a crown of thorns when he acknowledged to Pilate that he was king of the Jews (see Matthew 27:29; Hebrews 2:7).

Paul, in his preaching refers to this laurel wreath as a symbol of those who would win the race of life (see 1 Corinthians 9:24-27).

"...I have finished the race, I have kept the faith. Now there is in store for me the crown of righteousness, which the Lord, the righteous judge, will award to me on that day-and not only to me, but also to all who have longed for his appearing." (2 Timothy 4:7-8).