Blob some onto a penny, smooth down the edges and poke a hole in the middle:
Add your terrain-texturing material; in my case brown-tinted tile grout:
Allow to dry, paint and dry-brush. Result: bases for flags to mark terrain captured or scenario objectives.
Or you can use spare Green Stuff to attach bits of dry twig to a penny. Two shown here with the base already textured and painted:
Dry-brush base, glue on clump foliage and voila, 6mm trees:
Finally, with several batches of left-over Green Stuff you can gradually build up this kind of thing, again on a penny:
Paint orange/yellow, glue on cotton wool or paint-dyed interfacing material and you have a 6mm scale explosion marker: