Here's the best way to do it for future use.
Go to the folder in which Guild Wars is installed (by default C:\Program Files\Guild Wars\gw.exe - but somewhere else if you're sensible) - right-click on gw.exe and select Send to -> Desktop (create shortcut.)
Right-click your new shortcut and select "Properties"
Go to the Shortcut tab (should already be up)
In the target box, it will say "C:\Program Files\Guild Wars\gw.exe" - just add a space after the final " and type -image. Click ok and you're good to go - you may want to rename the shortcut to GW - image or similar.
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