I’ve updated the recent achievements image script to have another option. You can now choose the width of the image by adding width=<# of pixels> to the URL.
Like so:
[img]http://www.yourfirefly.com/wow/achievements.php?image&character=Slippir&realm=Mug'thol®ion=us&faction=alliance&width=440[/img]
the above code produces the following…