How to get the image on my 404-page display in original size (width)

Hi, I’m using Vantage Premium / Full-Width-Page and use your 404-Template.

The 404 Page shows:
1. the menu on top
2. one line text
3. an image

Problem: the image is automatically resized to 770px (width).

Question: How can I get the image display in original size? As I do not use a sidebar there is many free space on the right side of the page.

Here the 404-Code:

URL: http://www.fotostudio-cezanne.de/