So, lots of us have the GW IG Heavy Weapons teams. Which, once you've built your one heavy weapon team, leaves you with five spare weapons. If you don't mount your missile teams on the stabilising stand, that leaves you with the bits to assemble a mortar baseplate. So with another 60mm base, that's another heavy weapon.
The dent bits to put the little men are 25mm electrical conduit. Very easy to cut down with a scalpel or knife (doesn't need to be too sharp, either, this stuff cuts like something deliberately designed and manufactured to be easy to cut - funny that), but not super easy to keep an exact line - but I fill up to the rim (from the outside) with filler anyway, so it doesn't need to be too fine a tolerance.
And slap on sandbags, bombs and so on; that's mortars in ubiquitan army green for any army short of supporting firepower.
So, using some handy Valhallans, this should give you an idea of what you get. Las-cannons up next !