From The TimeSplitters Wiki

Decoratives are objects that can be placed in mapmaker to add variety to a level. They cannot be collected or interacted with, but they help to make a map feel more 'well-made'. The exact nature of the item varies depending on the tileset it is placed in. Decoratives are only available in TS3.

Military: A helmet on the end of a rifle standing vertically up from the ground. Even though the rifle is clearly the game's Soviet Rifle, it cannot be collected or otherwise used in any way.

Lab: A microwave-like machine on a stand, reminiscent of a Star Trek replicator.

Horror: A stuffed bear.

Egyptian: A garish golden statue.

Virtual: A blue and red virtual version of the lab object.