When you install the TigerVNC on RHEL7/Centos7, maybe work normal by  follow step:

[root@frank yum.repos.d]# yum install tigervnc-server.x86_64 
[root@frank yum.repos.d]# cp /lib/systemd/system/vncserver@.service /etc/systemd/system/vncserver@:1.service
[root@frank yum.repos.d]# vim /etc/systemd/system/vncserver@:1.service 
ExecStart=/sbin/runuser -l root -c "/usr/bin/vncserver %i -geometry 1024x768"
PIDFile=/home/root/.vnc/%H%i.pid
[root@frank yum.repos.d]# systemctl disable firewalld.service

But I found more issue and report alarms(that waste long time!!!), follow only one issue:

[root@frank system]# systemctl status vncserver@3.service
vncserver@3.service - Remote desktop service (VNC)
   Loaded: loaded (/usr/lib/systemd/system/vncserver@.service; enabled)
   Active: failed (Result: exit-code) since Wed 2014-10-01 18:26:26 EDT; 5s ago
  Process: 8771 ExecStart=/sbin/runuser -l  -c /usr/bin/vncserver %i (code=exited, status=1/FAILURE)
  Process: 8768 ExecStartPre=/bin/sh -c /usr/bin/vncserver -kill %i > /dev/null 2>&1 || : (code=exited, status=0/SUCCESS)

Oct 01 18:26:26 frank runuser[8771]: runuser: user  does not exist
Oct 01 18:26:26 frank systemd[1]: vncserver@3.service: control process exited, code=exited status=1
Oct 01 18:26:26 frank systemd[1]: Failed to start Remote desktop service (VNC).
Oct 01 18:26:26 frank systemd[1]: Unit vncserver@3.service entered failed state.

So I give up use systemctl to control vnc, I change follow way that resolved vnc auto reload after chassis reboot. In RHEL7/Centos7, default remove execute permissions for /etc/rc.d/rc.local, so if you use the way, you need change it:

[root@frank rc.d]# chmod 777 rc.local
[root@frank rc.d]# vim rc.local 
/sbin/runuser -l root -c /usr/bin/vncserver :1
/sbin/runuser -l cisco -c /usr/bin/vncserver :2

After reboot RHEL7, you will found VNC normal work.