MacOS – Gray globe (earth) appears after restart for no apparent reason – might something be wrong

I've had the exact same problem before with my Mid-2010 MacBook Pro. I took it into the Apple support people on campus and, after running quite a few tests, they found out that the cable connecting the AirPort card to the motherboard had gone bad. It sounds like this is the same thing that you're experiencing, so your best bet is to see about getting that cable replaced.

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 < 0 then
    set mypicturenumber to (288 + mypicturenumber)
end if
set picnumber to 0
if mypicturenumber > 99 then
    set picnumber to "0" & mypicturenumber
end if

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

launchd file "com.individual.Background.plist"

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

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.