2015-04-22 - i want to change log in page with my photo

Header Data

From: Min Thein <mi***u@gmail.com>
Message Hash: 68156dbbbba272ef7f284dd319f56b303913506907afea749076f0ce25ce77f1
Message ID: <187c8a13-6593-4ce8-b794-0a5d9435ef07@grasehotspot.org>
Reply To: N/A
UTC Datetime: 2015-04-22 03:54:26 UTC
Raw Date: Wed, 22 Apr 2015 03:54:26 -0700

Raw message 

Dear All , 
             I want to upload the photo as log in page background. But i 
don't know how to do  it ?
If anyone know that issue please let me know how to fix it ?
I uploaded my photos to usr/share/grase/www/images folder. and i changed 
main css like it (please check in my attachment).
but nothing is appear in my page background. I am really in trouble. Please 
help me please.

With Deep Respect,
Minn Thein

I hope you can help me to fix that issue.
Thank you very much.

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