If you do not find what you need at CGTextures (an excellent source of free textures) or need out of the box tileable textures, check out these texture packages at DAZ.
http://www.daz3d.com/i.x/shop/itemdetails/-/?item=3360
http://www.daz3d.com/i.x/shop/itemdetails/-/?item=3359
http://www.daz3d.com/i.x/shop/itemdetails/-/?item=2543
The kits are $1.99 for platinum club members.
I have the Dark Design ones and find them quite interesting. They include a few cobblestones and wall textures which are typically 1500 by 1500 pixels. There are ready made bump maps for some of them. They also have lots of architectural details to add, if you plan to do so.

Here is a picture made using the dark design wall texture (rendered in Bryce). I turned it into a terrain before, using the technique I describe in this Bryce tutorial (it works the same way in Vue)

Fantasy pictures, free 3d models, 3d tutorials and seamless textures on Virtual Lands.