Jesus crown of thorns is a vastly discussed subject. I do not want to repeat others in their study of this matter, but rather, would like to say several important things which will help us appreciate even more what Jesus did for us.
First of all, thorns were a part of the initial curse upon man:
"And unto Adam God said, Because thou hast hearkened unto the voice of thy wife, and hast eaten of the tree, of which I commanded thee, saying, Thou shalt not eat of it: cursed is the ground for thy sake; in sorrow shalt thou eat of it all the days of thy life; Thorns also and thistles shall it bring forth to thee; and thou shalt eat the herb of the field..." (Genesis 3:17-18)
Second, the Lord pictured the natural enemies of Israel as thorns in Numbers 33:55; Joshua 23:13 and Judges 2:3.
Third, apostle Paul mentions as a thorn in his flesh, and identifies it with a messenger of satan (2 Corinthians 12:7)
These 3 points above pretty well sup it up. Natural and spiritual curse, natural and spiritual enemies. And they placed a crown of thorns on Jesus head. The Crown is a symbol of rulership, so how would you like something to be placed upon you, which is a symbol of the rulership of the curse and your enemies?
Well, Jesus endured exactly that - He became sin and He gave the darkness its hour to "dominate and rule" - to strike Him with every curse, every sin, every sickness, and He bore the punishment of all this in His Own Body - FOR US! Won't you be forever grateful for that?