Edit Custom Headers link when upload complete

Hi folks,

my problem is , " How can I rewrite custom-headers links,when upload completed."

when users add new media,
file links like this: http://cdn.lettoblog.com/mustafa/files/staff.jpg and also this file storege on web server (http://mustafa.lettoblog.com/files/staff.jpg ),but we delete periodically.So we'r using link from cloud.

but when users upload custom-header media links shows on web servers link.I wanna edit links address.

for example,
http://mustafa.lettoblog.com/files/cropped-Lighthouse.jpg = http://cdn.lettoblog.com/mustafa/files/cropped-Lighthouse.jpg

How can I edit custom-header's url?

Any idea or advice?

Thanks.