How can I include a new marvel of the world?

[GiantMonkeyMan]

you mean like the pyramids/the hanging gardens?
well it is actually quite difficult to make a completely new wonder that appears on the campaign map... but if you find one of the building tutorials and just make your wonder like that (like EB has done) you can make your wonder not buildable by anyone and then put them in decr_strat in the correct province/town with whatever bonuses you want

GMM

[Dol Guldur]

You cannot have an 8th Wonder in game terms, though you can certainly replace an existing one.

[GiantMonkeyMan]

i was thinking about this after i posted... could you make a new resource image (you know like they made the fish and meat ones for RTR) that looks like your new 'wonder' on the campaign and then have a building to represent it, along with a custom tile for when you fight around that region?

that would be sooo cool
GMM

[Dol Guldur]

Yes, you can - the advantage of the visible resource model is that it, unlike the Wonder model, is passable so it can be placed in a passage such as over a bridge. A unique building can then be used to represent it and the faction_capability can be used to create a faction-wide effect should you require it. We've taken this a stage further in the Fourth Age but you'll just have to wait and see ;)

The disadvantage is that there is no Wonder trigger of course.