Okay, I think I have it.  You need to make changes to two files.  In
{TDE}/share/apps/konqueror/about/intro.html , change
 
    <div id="headerL"/>
    <div id="headerR"/>
 
to
 
    <div id="headerL"/>
    <div id="headerCenter"/>
    <div id="headerR"/>
 
This surgery is also going to have to be performed on most of the other HTML
files in the same directory--all but one of them use the same header.
 
Then go to the first stylesheet (kde_infopage.css on my system, might be
tde_infopage.css or the like on yours) and patch it with the attached
.diff file.
 
After that, you should have a new headerCenter div that displays the background 
stripe only where you want it.
 
If this doesn't work, there's some kind of file regeneration step missing--I
saved off a copy of the page instead of trying to work with the system files.
 
E. Liddell

Thank you for your great work! It works right as it should! The new transparent picture with the ribbon is not yet 100% like I want it, but it gives a good idea of what it would be.

I personally definitely like the one with the toned-down Crystal-fire background. It is more in style with classic KDE 3.5.10.2, so it won't hurt too much the more conservative users :), while providing something less flat, with a texture. It also fits much better with the actual ribbon, which I still have to work on, to make it integrate well with any picture.

I still have to check out why does ''Akregator'' and ''Help'' does not uses the regular TDEUI files, and uses their own ones.

Also, Michele talked about transforming the bar, under the top part, into a box, just like the middle box. I tried to adapt the file to transform it in a box, by comparing the text, but for an unknown reason, the transparency doesn't work around the rounded corners, just as on the middle box. Is there something to do about it?

Tell me which one you prefer! Or if you want to submit another background, to check what it would look like.
-Alexandre