Minor suggestion: Change item models to something other than the gold chest. I mean, imagine this: 'Look, a chest full of gold! Ooooh, it morphed into a Viking Sword!' Although this might be cool in real life, here it isn't. lol
Some real interactable terrain suggestions:
Falling trees and columns are always nice. Same goes for destructible crates and barrels.
Forest Pond - a flood would be great here. It would make you climb to the upper part of the map, thus making you fight instantly. The flood, and falling trees.
Island - pirate attacks. Maybe sounds stupid, probably because it is. You make a ship and make some cannonball projectiles from it. Falling trees here, also.
Tavern - aside from destructible tables, chairs and columns, here's one more idea: destructible bottles. Randomly spawns different potions, and destroying them either buffs or debuffs nearby swordsmen.
...I can't think of anything else that would suit your terrains right now, bit I will tell you as soon as I figure it out.
Game mode suggestion:
War - playable on Battle Zone ONLY. Team fight. Apart from swordsmen, every team gets an army. 4 types of units: Foot Soldier, Marksmen, Horsemen and Pikeman. Can kick out anyone if you want (I mean unit types, when making them). Last team standing wins.