Max Width Image

Add the image to your wiki page:

<div class="res-img">
[[File:Whatever.JPG]]
</div>

Make a class for responsive images, i.e. insert the following in your MediaWiki:Common.css

/* To make images responsive */
.res-img img {
	max-width:100%;
	height:auto;
}

Linking within a Page - Anchor

Define the anchor

<div id="NameOfAnchorHere">optional text</div>

Reference the anchor

[[#NameOfAnchorHere| test]]

If the div causes a line break you may want to use:

<div id="NameOfAnchorHere" style="display:inline;"></div>

Reference	URL
How to make an image simply size to the users screen?	https://www.mediawiki.org/wiki/Topic:Tuubagqalz9vk2m9
Mediawiki link within the page to a specific place, rather than a section	https://stackoverflow.com/questions/23656415/mediawiki-link-within-the-page-to-a-specific-place-rather-than-a-section