When we are looking to create objects in forge we will basically try to make items that can be used in various ways. So we will usually start with basic primitives such as a box or cylinder then we will move onto items like walls and bridges. We will also try and make things that match the map that they are being placed in as best as possible. For example the objects in Foundry were built with the specifications set by the map layout. But they had to be versatile enough that players can move things around to make all types of scenarios. We also try to think of goofy or cool things we would like to set up and do when we customize our own maps. So then we will make a few other objects based upon ideas folks have.

[...]

To clarify this a bit further, the Screen Filters are placed on a map in Forge. The object itself (the sphere above) is invisible during gameplay, but the object's effect is completely visible during gameplay, once it has been placed on the map. So I could place "Gloomy" on Avalanche in Forge, save it as Lukealanche and then when you play Lukealanche it will have the gloomy effect during actual gameplay. These are not post processing effects, they are applied live, in real time to the game you're playing.