Following the instructions on specifying an image as the thumbnail for Sphinx galleries, I encountered some strange behavior.

• First, the path for rendering the image in the gallery (.. figure:: ../../_images/agrivoltaics_system.jpg) differs from the path used for the thumbnail (# sphinx_gallery_thumbnail_path = '_images/agrivoltaics_system.jpg'). It seems counterintuitive that the paths for these should be different.

• Second, when the sphinx_gallery_thumbnail_path does not find an image, it uses a placeholder image but does not raise a warning that the image was not found.

The specific example can be found here: pvlib/pvlib-python#2459