The image size is stored where the graphic is being used (as you can use the same graphic multiple times at different sizes), in the a:graphic tag in line to where the image is being used. Instead of the data being here, like earlier, this now points to a relationship ID.
The list of relationships are in the top of the file, one of them you find will have a type of 'image'.
The attributes of the Relationship will be the name of the target (such as media/image1.jpeg). This is a link to the binary of your image, and will be located later on in a pkg:part/pkg:binaryData element.
It looks a bit like this:
<Relationships xmlns="http://schemas.openxmlformats.org/package/2006/relationships">
<Relationship Id="rId8" Target="media/image1.jpeg" Type="http://schemas.openxmlformats.org/officeDocument/2006/relationships/image" />
.. other relationships
</Relationships>
.. lots more document
<pkg:part pkg:name="/word/media/image1.jpeg" pkg:contentType="image/jpeg" pkg:compression="store">
<pkg:binaryData>/9j/7QAsUGhvdG9zaG9wIDMuMAA....blah
</pkg:part>
.. lots more document
<w:drawing>
<wp:inline distT="0" distB="0" distL="0" distR="0">
<wp:extent cx="2266950" cy="1543050"/>
<wp:effectExtent l="19050" t="0" r="0" b="0"/>
<wp:cNvGraphicFramePr>
<a:graphicData uri="http://schemas.openxmlformats.org/drawingml/2006/picture">
<pic:pic xmlns:pic="http://schemas.openxmlformats.org/drawingml/2006/picture">
<a:blip r:embed="rId8" cstate="print"/>
<a:ext cx="2266950" cy="1543050"/>
.. lots more document