To make blueberry simple syrup, combine blueberries, maple syrup and juice of 1 lemon in a small sauce pan. Bring to a boil, reduce heat and simmer until blueberries have broken down (about 3 minutes). Strain blueberries through a sieve or cheesecloth, allow to cool. In a large pitcher, whisk together juice of 4 lemons, seltzer and blueberry simple syrup. Add alcohol if desired and whisk to combine. Refrigerate for at least 1 hour. Serve over ice and add extra blueberries if desired.