Static effects are things you can add to your map that don't have a model and can't be interacted with. You add them using:
*addstaticeffect [EFFECT_NUM],[WORLD_X],[WORLD_Y]
Supported values for [EFFECT_NUM] are:
0 : Streetlight
1 : Campfire
2 : Campfire with smoke
3 : Smoke (without fire)
4 : Black Smoke
5 : White smoke
6 : Gentle grey smoke
7 : Gentle black smoke
8 : Gentle white smoke
9 : Configurable streetlight 1
10 : Configurable streetlight 2
11 : Configurable streetlight 3
12 : Configurable streetlight 4
13 : Spotlight (Directional light pointing up)
14 : Tree stump
To remove all static effects from the map:
*delallstaticeffects
An alternative option to using static effects is to add backgroundmodels or ornamental buildings that have effects attached to them using the Model Converter. This has the advantage of giving you more direct control of the location of the effect.