KWin Script: When Gimp image window is activated raise toolbox and docks of Gimp. When image window is not active anymore toolbox and docks are lowered again.
Note probably needs KDE 4.9 and higher due to API changes between 4.8 and 4.9.
Installation instructions for scripts can be found at http://techbase.kde.org/Development/Tutorials/KWin/Scripting#Packaging_KWin_Scripts