Hell, someone else needs to do some work too!!
I take it most of you have already seen
these.
It's not that many tiles, mostly it's ground decals. I think i have explained this before - i just use a dummy structure, which has no model, pathing, or selectability, and then i just use a ground texture for it which i have replaced with something custom. After that, i use these as doodads to paint the ground with high-res textures.
I am attaching the files below. Some other skins and models can be found in the thread for Ancient Empires (a project made by Pson). I am not sure how well they will look together with regular water, in the screenshot i replaced all water textures with empty textures, and instead used a massive modified version of the water plane which covers the entire map. This modification can be done with notepad.