Best way to make something look like cave/underground

Whats the best way to add a "roof" to terrain to make it look like your in a cave or underground. I downloaded the ultimate terraining map and have used the underground roof section from this, but i need another variation now are there any other "roofs" around that can be used?

I dont really think so, but you might use the underground Dome or what its called, that allready exist in the WE from before the UTM

use archways

Using this model package could help.

Thick black fog + completely tinted black flat doodads on the ceiling. It makes it look like there is a ceiling but you just can't see it.

Or upside down darkened lordaeron variation 8 rocks, flattened and widened.

Void, how do you make a doodad flat?

You do that by modifying the X,Y and Z values for the doodad.

[offtopic]Firewind is awesome [/offtopic]

~Deathcom3s