This configuration is enough:
#for main location
location / {
try_files $uri $uri/ /index.php;
}
#for admin panel (if you are using custom admin directory you have to modify this path)
location ^~ /admin {
try_files $uri $uri/ /admin/index.php;
}
Of course it is only rewrite rules config, You have to also set up php-fpm.
Of course it is describe in the documentation.
http://docs.whmcs.com/Version_6.0_Release_Notes#New_Location_for_Custom_Logo_Files
If you have once of these files:
/assets/img/logo.png
/assets/img/logo.jpg
$assetLogoPath is set.