The Adoration of the Lamb of God, from the Ghent Altarpiece by van Eyck. A fine portrayal of the Heavenly Liturgy working in tandem with the Mass on Earth.
Thank you, kkollwitz: it's one of my favorites. And to you, Oddyoddyo13, I write the words that Our Blessed Lord spoke to His apostles when He still walked this earth: "Your sorrow will be turned into joy." Thank you both for your comments, and may God bless you.