The image template special:img allows you to add inline images to a wiki page. It has more options than the simple inlining via a bracket link.
Every image template must have two parameters: a text describing the image and the URL of the image itself. Both parameters are anonymous parameters, the description comes first (like in bracket links):
{{special:img | a short description | http://senseis.xmp.net/images/stone-happy.png }}
The description is put into the HTML alt and title attributes.
Other (optional) parameters are:
A basic image (short syntax):
{{:img | happy stone | http://senseis.xmp.net/images/stone-happy.png }}
yields:
Using a thumbnail image and link to another page:
{{:img | atari | atari:i | link=Calling Out Atari}}
Adding a caption to an image, floating on left side:
{{:img | goban | http://senseis.xmp.net/images/goban-alignright.jpg | caption=A game in progress | float=left}}
The following text floats around the image. Use 4-% to clear the floating, like you do, when forcing a text below a diagram.