I have modified Klaus-Juergen's proposed designs and put my versions here:
https://wiki.documentfoundation.org/Documentation/Development/TemplateForV4
(GS samples in PNG, plus source files in SVG)
and here: http://www.odfauthors.org/libreoffice/english/getting-started/draft-lo-4.0
(GS sample only, PNG)
Notes regarding the back cover: I've left quite a bit of blank space
at the bottom for the barcode, and I have removed the footer text,
which would have been partially obscured by the barcode when the cover
is reduced from A4 to 6x9-inch size for the printed books. I may
further modify the text.
K-J: Please note that the label "Impress" is missing from one of the
icons in the row of icons on the back and front cover. I added it on
the GS front cover, but I have not yet added it on the other versions
of the row of icons because I wasn't sure how to do that where it is
greyed. (I'm not very experienced with using Inkscape or other SVG
editors.)
Yes, I know that decisions regarding v4.0 branding may mean that these
covers will be a bit out of date. However, I'm running out of time and
wanted to have something to use. It's easy to substitute covers later,
if necessary.
Comments welcome.
--Jean