Allow Binary Files

If you allow binary content (such as images), you have two possibilities:

You can upload and use images on wiki-pages. When editing a page, an upload form will be displayed for uploading images. After a successful upload, an image code is displayed that you can embed in your pages using square brackets. For example: [internal://myimage.gif].
You can attach files to a Wiki Page which can be displayed by the attachments action. The size is limited to the setting made in Moodle.