Was something supposed to happen? When you beat the Dragon in Minecraft, does anything happen? The credits maybe, but would you want to see that in Valheim? There's not much that can be done, even if the game was released. What do you think should happen?

There's actually something significant that does happen when you place all the boss heads down, the world becomes more challenging. Fulings spawn anywhere, and all the invasions will occur, and 2* enemies will be more frequent. Sadly you probably have 100 armor and nothing can touch you so, not really a big improvement.