Preheat oven to 350 degrees. Put cranberries into a large, high-sided skillet; set aside. Bring syrup, wine, brown sugar, vanilla bean and seeds, lemon zest, peppercorns, and salt to a boil in a medium saucepan, whisking occasionally.
Pour over cranberries. Cover tightly with foil, and bake until cranberries are soft but have not burst, about 10 minutes. Using a slotted spoon, transfer cranberries to a bowl; cover with 1 cup cooking liquid. Let cool completely.
Bring 1/2 cup cooking liquid and the granulated sugar to a boil in a small saucepan, whisking until sugar has dissolved. Reduce heat to low; simmer until liquid has reduced and barely coats the back of a spoon, about 6 minutes. Pour through a fine sieve into a medium bowl; let cool completely. Syrup can be refrigerated in an airtight container until ready to use, up to 3 days.
Reserve 40 cranberries. Puree remaining cranberries and liquid in a blender.
To serve, place 10 reserved cranberries on each of 4 decorative skewers. Pour 1/4 cup puree and 1/4 cup syrup into each of four 12-ounce glasses; stir to combine. Add skewers, and fill glasses with ice. Top with seltzer, and serve.