In trunk/zkwebui/theme/default there are a couple of files: login-left.zul, vendor-logo.zul, version-info.zul etc.
File version-info.zul contains the server info data. You can change these files so the login page appears as you please.
In file vendor-logo.zul there is the possibility of customization to own logo, links etc.
Configuring the files in trunk/zkwebui/theme/default enables you to change the appearance of the webui login page to your needs.
A build is needed.