The Textures overrides parameters control whether V-Ray will render textures in your scene and/or filter them.

Maps – Enables (default) or disables texture maps. This option is useful for troubleshooting renderings, for example for determining the extent to which texture maps are contributing to noise or other rendering artifacts.

Filter Maps – Enables (default) or disables texture map filtering. When enabled, the depth is controlled locally by the settings of the texture maps. When disabled, no filtering is performed. 

Max Mipmap Resolution – Sets the maximum resolution for mipmaped files. All planes with higher resolution from the file won't be used. If set to zero, the original file resolution is used.