go to here;
http://www.riotcreative.co.uk/tools/AlpineConverter.aspx
take whatever picture you want off your HDD and this tool will size it convert it to APN and even show you what it will look like on the HU...I have made 11 APN's with this for my X-100 and they all work perfectly...
One thing though, when you hit the download button it will go to a wrong page, so once you get to that page then hit the go back arrow on your comp and it will come up with a screen that says " webpage has expired" once there hit refresh and it will take you back to the correct page, then hit download again, it will have an area to fill out info and description of pic and hit the download button again and save it to your hdd...
make sure you put something descriptive in the pic title or you won't know which background...
Also you can go to;
http://www.pride-rock.com/forum/apnlist.php?mode=joined&order=DESC&start=1200
and all those pics are already made into APN's but none of them would work for me...You might have better luck with them but I did steal some of the pics off that site and converted them with the APN tool...GL and if you need any more help PM me...