Starting with the easiest one first - this is sea glass glued in a shadow box. I could totally do this and I even have a sea glass collection to use.
Kate's Paperie is an online source for hand made papers. OR you can go to Natural Curiosities and pay a few hundred for one, which makes the DIY version so.much.better.
If you're in to abstract art, I think anyone could create this type of painting with a ruler on canvas.
Channel your inner child with this. Hot glue crayons to the canvas and then blow dry. You could use all blues and greys for a moody canvas or coordinate with the colors in your room for that custom over-the-sofa painting.