There was a proposal in Latvia and Estonia to be annexed by Sweden, so regaining that portion of the Swedish empire is possible. Obviously Finland can perhaps be regained. Likewise, Sweden's territories in Germany might be retained with a different ending to the Napoleonic Wars. Sweden can keep St. Barts in the Caribbean, and also Guadeloupe. Likewise, Sweden might be able to pick up a part of Africa or two assuming we have a Scramble for Africa-type event TTL, and probably Asia as well. And I don't know if this would count, but Sweden leading the way in Scandinavianism with Denmark-Norway uniting with it to form a "United Kingdoms of Scandinavia" (with the capital at Gothenburg perhaps) might be doable as well.