activities and scripting

hi , i have an issue with plasma and it's this :

i have created some wallpapers with different resolution made in this way :

usr/share/wallpapers

── fabric-gnome
│ ├── contents
│ │ └── images
│ │ ├── 1024x600.png
│ │ ├── 1024x768.png
│ │ ├── 1152x864.png
│ │ ├── 1280x1024.png
│ │ ├── 1280x720.png
│ │ ├── 1280x768.png
│ │ ├── 1280x800.png
│ │ ├── 1280x960.png
│ │ ├── 1360x768.png
│ │ ├── 1366x768.png
│ │ ├── 1400x1050.png
│ │ ├── 1440x900.png
│ │ ├── 1600x1200.png
│ │ ├── 1600x900.png
│ │ ├── 1680x1050.png
│ │ ├── 1920x1080.png
│ │ ├── 1920x1200.png
│ │ ├── 2048x1152.png
│ │ ├── 2560x1440.png
│ │ ├── 2560x1600.png
│ │ ├── 640x480.png
│ │ └── 800x600.png
│ └── metadata.desktop

this code :

https://code.google.com/p/kde-peace-settings/source/browse/Plama-Panels-Collection/usr/share/kde4/apps/plasma/layout-templates/org.kde.plasma-desktop.gnome3Activity/contents/layout.js

works but it has some kind of bad behavior like this

http://wstaw.org/m/2013/12/09/plasma-desktopA27453.png

and when you get the whole desktop filled by the png file you get a
wrong resolution

instead this code works ...

https://code.google.com/p/kde-peace-settings/source/browse/Plama-Panels-Collection%20wallpaper/usr/share/kde4/apps/plasma/layout-templates/org.kde.plasma-desktop.gnome3Activity/contents/layout.js

i thought that plasma would do that automatically :S or i am doing it wrong ?