sample configuration profile to set the desktop picture.

desktop_picture_boringblue.mobileconfig

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
	<key>PayloadContent</key>
	<array>
		<dict>
			<key>PayloadDisplayName</key>
			<string>Desktop</string>
			<key>PayloadEnabled</key>
			<true/>
			<key>PayloadIdentifier</key>
			<string>com.scriptingosx.desktoppicture.boringblue</string>
			<key>PayloadType</key>
			<string>com.apple.desktop</string>
			<key>PayloadUUID</key>
			<string>6A2D7927-44FC-4109-9B5B-7DB2F0E99C38</string>
			<key>PayloadVersion</key>
			<integer>1</integer>
			<key>override-picture-path</key>
			<string>/Library/Desktop Pictures/BoringBlueDesktop.png</string>
		</dict>
	</array>
	<key>PayloadDescription</key>
	<string>Locks the Desktop Picture to Aqua Blue</string>
	<key>PayloadDisplayName</key>
	<string>Desktop Picture - Boring Blue</string>
	<key>PayloadIdentifier</key>
	<string>com.scriptingosx.desktoppicture</string>
	<key>PayloadOrganization</key>
	<string>Scripting OS X</string>
	<key>PayloadRemovalDisallowed</key>
	<false/>
	<key>PayloadScope</key>
	<string>System</string>
	<key>PayloadType</key>
	<string>Configuration</string>
	<key>PayloadUUID</key>
	<string>AAE8D4EA-0FAE-4A3B-BB2D-15B1CD13DC05</string>
	<key>PayloadVersion</key>
	<integer>1</integer>
</dict>
</plist>