Thanks Avinoam for confirming it works.
Closing report.

gl2ps has been patched and the current development version produces properly scaled images. AFAIU there will be a a release of gl2ps soon [1].

I think we can close this report as it has been fixed upstream

[1] http://www.geuz.org/pipermail/gl2ps/2015/000421.html

Alas, I'm not certain this isn't an Octave bug with the printing of 'image' data to svg.  I used rectangle() to create 4 differently-colored boxes on an ordinary plot background.  When I print this the svg is correct.  I'm attaching that file as svg_rect_tst.m

Secondly, the white polygons are present at the beginning of every svg file.  They represent the axis background.  You can verify this with

set (gca, "color", [0.5 0.5 0.5]);
print foo.svg

Now I get the following in the svg file.

<polygon fill="#7f7f7f" points="521.28,384.48 521.28,32.4 521.28,384.48"/>
<polygon fill="#7f7f7f" points="521.28,32.4 521.28,32.4 521.28,384.48"/>
<polygon fill="#7f7f7f" points="74.88,32.4 521.28,32.4 74.88,32.4"/>
<polygon fill="#7f7f7f" points="521.28,32.4 521.28,32.4 74.88,32.4"/>
<polygon fill="#7f7f7f" points="74.88,384.48 521.28,384.48 74.88,32.4"/>
<polygon fill="#7f7f7f" points="521.28,384.48 521.28,32.4 74.88,32.4"/>

(file #27540)

image(x=1:2, y=1:2, x'*y);
print foo.svg

produces incorrect output (basically an empty figure).