-You can also set default values that will be applied to all later images on
-the page, unless overridden. Useful when including many images on a page.
+The `size` parameter is optional, defaulting to full size. Note that the
+original image's aspect ratio is always preserved, even if this means
+making the image smaller than the specified size.
+
+You can also pass `alt`, `title`, `class` and `id` parameters. These are
+passed through unchanged to the html img tag. If you include a `caption`
+parameter, the caption will be displayed centered beneath the image.