KDE artwork : reuse of icons under GPL-2 ?

Hi, and happy new year :)

I would like to (slightly) modify and reuse some icons from various KDE packages (mostly "crystalsvg", "hicolor" and "oxygen"
icons, provided by kdebase-data or kdeartwork-iconthemes from Gentoo) in some applications. Some of these packages - and icons -
are under GPL-2 license (right ?).

I've read that using some work under GPL-2 implies the entire new application to be under GPL. The problem is, I _have_ to use
another license for our apps (CeCILL-B, a french license for education :
http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.html).

What is the best solution ?
- to use only LGPL*-only icons ? (time consuming, but I guess it would be ok)

- to ask the permission to include all these icons in our package under our own license ? Who should I ask that to when I'm not
sure about the designers of each icons theme (oxygen and crystalsvg are pretty obvious, but what about 'slick', 'hicolor', ...
ones ?)

- to build a separate package under GPL-2 including these icons, then ask users to download both packages to "rebuild" the
application ?


I've read many posts and docs about licensing, but I still don't have a clear answer.

Thanks for your help !


Regards,

--
Christophe