I have my own image which i want to set as wallpaper to KDE4 Desktop.

KDE4 wallpapers are stored in directory
/usr/local/kde4/share/wallpapers

Now go to directory
cd /usr/local/kde4/share/wallpapers

Now make directory with desired name
mkdir Example_001

Following should be the structure of your directory

Example_001
  |
  |--contents
  |----images
  |
  |--------1024x768.jpg
  |--------1280x1024.jpg
  |--------1280x800.jpg
  |--------1440x900.jpg
  |--------1600x1200.jpg
  |--------1920x1080.jpg
  |--------1920x1200.jpg
  |--------800x600.jpg
  |
  |----screenshot.jpg
  |--metadata.desktop

screenshot.jpg is a used for showcasing it in desktop settings

In `images`  directory you need to save images as per size indicated by name so that kde4 can get select image as per resolution.

Now we to write content for metadata.desktop file

[Desktop Entry]
Name=Name for wallpaper

X-KDE-PluginInfo-Name=Name for Plugin
X-KDE-PluginInfo-Author=Author Name
X-KDE-PluginInfo-Email=Email of Auther

You can check the information about wallpaper and set it to your environment