Never received my 'Surfbreaker' shader on my warlock when I reached level 40, wasn't even aware it was a reward until I saw a friend with it on and when I was helping my cousin level his warlock last night he got that shader as a reward when he reached level 40 and turned the quest into Ikora Rey, I've asked other friends where they got theirs and they all told me it was from the 'Reach Level 40' quest