they would have to be pretty epic battles and is positions that a fight can not be avoided, such as a gate or river tile. If it's implemented i think there should also be a boost for cities (higher moral for defenders or something)

Excellent idea, and I personally like the idea of the momument/tile to be in the same exact spot as the battle, instead of choosing it.  Of course, that's just one man's opinion.  It could end up being a very cool feature if a map features nature chokepoints and these epic battles are taking place around the same few tiles.

I'm more open to the tile idea, rather than the monument as I'd like to think my troops have a sense of history and don't need some marker just to fire them up.  That and if a monument got descrated by the enemy, I would think that anger my troops and make them fight harder, instead of losing their advantages. 

If morale was a big feature of this game (and I hope it is), I think that should be the most likely bonus from these battle tiles.  I can understand how it would give troops a better morale to be fighting on the spot of some past battle, but how is that going to make them shoot arrows more accurately?

I remember i game implementing a such feature (I don't remember its name)

Epic battle are symbolised by crossed swords and putting the mouse over gave us more information like When, Who were the 2 sides involved, their leaders and the outcome.

Maybe it would wise to cross the Spoils of war & Battlefield tile.

Players can investigate former battlefields for leftover loots with sometime nasty surprises awating them. Like a golem that regenerate itself since a battle that happened a long time ago.

Left over loots would depends of the extra meterials no caried over and the random events monsters would depend of the nature of the defeated troops.

It's like treating every former battlefield like a new dungeon.

@vieuxchat

+1 the map must reflect the overuse of spells.