basically some of the options for FX that the GM can place down when it is added (I know I have posted a lot of numbered lists, sorry about that):

1. Artillery explosions (from mortars to artillery cannon fire, either singular or a zone which can drop a set amount or infinite)
2. Smoke clouds (from either smoke grenades, and as an option for artillery in option 1)
3. Tracer fire, either directed towards a ground target or randomly into the air
4. Flak bursts for the air