I sort of missed the release of Wave 2, not sure when it happened, but its here, and its awesome. You can still dig through and easily get wave 1, but now there is #19 through #37. And Wave 3 might be around the corner too!
The codes that are out are: 19 Hero thomas, 20 Classic Percy, 21 dinosaur James, 22 metallic Gordon, 23 metallic Edward, 24 classic salty, 25 old school spencer, 26 robo Toby, 27 classic diesel, 28 neon bash, 29 hero Hiro, 30 Classic Millie, 31 robo Charlie, 32 Classic Sidney, 33 dinosaur Ben, 34 classic skarloey, 35 old school Luke, 36 dinosaur, 37 classic Samson.
Wave 2 has a better assortment of characters and themes than wave 1 did too.
Pick a few up, they are highly detailed, and a pretty good price at about $2 a piece.