To change the logo and style, you have to use an extension. You can start with the zipping the contents
in this repo.
- zip -r /tmp/guacamole-branding-example.jar ./ inside the directory to create the jar file.
- Upload it using the File manager to /app/data/extensions
- Restart Guacaomole
The login screen should already be different now. You can now modify the guacamole-branding-example.jar as needed to make changes. Note that a jar file is just a zip archive. Just extract it, change files and compress it again. When re-creating the jar file, make sure that the files are at the top level and not inside a sub directory.