Width and height should be numeric values, the pixel prefix is automatically appended. The display mode changes whether the image should cover the whole [width x height] container, or should it be contained respecting the aspect ratio.
Background display mode
The plugin parses through the primary, then the alternative image sources, until it finds an image to display. If no image is found, the default image URL is used.
Image number for the parser
By default the first image is returned, whenever the parser finds an image within each source. This feature is useful, when for example there are multiple images within the post contents, and you want to skip the first N of them.
Exclude images by file names
Comma separated list of strings, whenever any of these is found, the image is skipped and the parser proceeds to the next possible image.