Buildings like: Gyms, Pixelmart, Pixelmon Center, a few NPC Houses maybe NPCs that give items, or ask for pokemon to trade.
And also having one always made where the player spawns, near the player, or some way to locate the "First" town. The first town would have a lab, where you pick your starters instead of the screen on the world load, a Pixelmon Center but no Pixelmart, and maybe a starter house acting as the players house with a "Mom" that gives running shoes.