Just run
# rpm -ql plesk-roundcube
Linux path
/usr/share/psa-roundcube/skins/classic/images/roundcube_logo.png
/usr/share/psa-roundcube/skins/larry/images/roundcube_logo.png
Image size
png width 178px height 47px
Attention in classroom
Just run
# rpm -ql plesk-roundcube
Linux path
/usr/share/psa-roundcube/skins/classic/images/roundcube_logo.png
/usr/share/psa-roundcube/skins/larry/images/roundcube_logo.png
Image size
png width 178px height 47px