Change background image with Time
Thank you for your input

So finally I managed to do it (at least I think so) 

I embedded an Applescript to change the background in a shell script which I added it to launchd.  

This is what it looks like:

Script "scriptly.sh"

#!/bin/bash
osascript -e '
set myhour to get the (hours of (current date))
set myminutes to get the (minutes of (current date))
set mypicturenumber to (myhour - 12) * 12 + myminutes / 5 as integer
if mypicturenumber &lt; 0 then
    set mypicturenumber to (288 + mypicturenumber)
end if
set picnumber to 0
if mypicturenumber &gt; 99 then
    set picnumber to "0" &amp; mypicturenumber
end if

if (99 ≥ mypicturenumber) = (9 &lt; mypicturenumber) then
    set picnumber to "00" &amp; mypicturenumber
end if
if 9 ≥ mypicturenumber then
    set picnumber to "000" &amp; mypicturenumber
end if
tell application "Finder"
    set desktop picture to {"Macintosh HD:users:USERNAME:Individualfile:backgrounds:earth:earth24h" &amp; picnumber &amp; ".png"} as alias
end tell
'


launchd file "com.individual.Background.plist"

&lt;?xml version="1.0" encoding="UTF-8"?&gt;
&lt;!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd"&gt;
&lt;plist version="1.0"&gt;
&lt;dict&gt;
    &lt;key&gt;Label&lt;/key&gt;
    &lt;string&gt;com.individual.Background&lt;/string&gt;
    &lt;key&gt;ProgramArguments&lt;/key&gt;
    &lt;array&gt;
        &lt;string&gt;/bin/sh&lt;/string&gt;
        &lt;string&gt;/Users/USERNAME/Individualfile/scriptly.sh&lt;/string&gt;
    &lt;/array&gt;
    &lt;key&gt;StartInterval&lt;/key&gt;
    &lt;integer&gt;300&lt;/integer&gt;
    &lt;key&gt;UserName&lt;/key&gt;
    &lt;string&gt;USERNAME&lt;/string&gt;
&lt;/dict&gt;
&lt;/plist&gt;


command to put it in action

launchctl load /Users/USERNAME/Individualfile/com.individual.Background.plist 

EDIT: 

The last command is there to load the script directly, however It will not be executed on startup. To do That you have to copy the file 

com.individual.Background.plist

to the ~/Libary/LaunchAgents/ folder.