Source: http://screwturn.net/Help.WikiMarkup-Pictures
[image:Name|Border|Location|Size|link=Link|alt=Alt|Caption]
Only Name is required. Most images should use "[image:Name|left|medium|alt=Alt|Caption]". The other details are optional and can be placed in any order.
Border
"border", "frame" or "frameless". Put a small border around the image. Default - "frame".
Location
"right", "left" or "auto". Determine the horizontal placement of the image on the page. This defaults to "auto" for thumbnails.
Size
"small" or "medium" or "full" or "maxXXX". "small" = 100 px width, "medium" = 100 px width, "maxXXX" = XXX px by max size of pictures. Default - "full".
Link
Link the image to a different resource, or to nothing. Must not be set for non-public domain images unless attribution is provided in some other fashion.
Alt
Specify the alt text for the image. This is intended for visually impaired readers.
Caption
Specify the image's caption.