This is so beautiful. The expression of surprise on her face, and the gentleness and kindness that Beren shows Luthien, it is captured so well in this work. If they ever make a movie about the Beren and Luthien story, it would be wonderful to have this interaction put in. It looks splendid.
When Tolkien created the story, his wife Edith was the inspiration for Luthien, dancing in a hemlock grove for her husband when he was on leave from the front lines of WWI. The way he described Edith dancing, in a letter to his son, was what started the love story. When Edith passed away, Tolkien had "Luthien" engraved under her name, and wished to have "Beren" engraved under his name when he passed and was buried next to his wife, so Beren would be forever reunited with his beloved Luthien. That, right there, is true love.