The Environment section in V-Ray render parameters is where you can specify a color or a texture map to be used during GI and reflection/refraction calculations. If you don't specify a color/map, then the background color and map specified in the SketchUp Environment dialog will be used by default.
UI Path: ||V-Ray Asset Editor|| > Render Settings > Environment rollout
Background – Sets a color or a map to act as a background during rendering. Press the checkerboard button to select a texture. If a texture is selected, it will override the selected color.
The above GI environment overrides have the following common controls:
Texture – Specifies a color or texture for the specified override. Note that Texture Enable must be enabled to have an effect on the scene.
Texture Enable – Enables or disables the specified GI texture.
The Environment settings section also includes a rollout for Environment Overrides and Aerial Perspective. Please see their dedicated pages for more details.