How to change WHM VPS Optimized logo to WHM logo
Steps:

Login via SSH to your VPS as root.
Goto "x" themes
cd /usr/local/cpanel/whostmgr/docroot/themes/x
Backup current logo
cp logo_vps.jpg logo_vps.jpg.backup
Change the logo
Choose one:

To WHM logo
cp -f logo.jpg logo_vps.jpg
To other logo
cp -f /path/other_logo.jpg logo_vps.jpg
To restore:

cp -f logo_vps.jpg.backup logo_vps.jpg
Good luck!