another example settings.py for rendermode-options

settings.py

rendermode = ['my-custom-mode']

custom_rendermodes = {
    'my-custom-mode' : {'parent' : 'cave', 
                     'description' : 'a custom mode that only renders certain depths',
                     'options' : {
                         #'depth_tinting' : False,
                         #'lighting' : True,
                         #'only_lit' : True,
                         'min_depth' : 40,
                         'max_depth' : 55,
                     }
    },
}