There is now a baseimage based on Guacamole stack located here:
https://github.com/linuxserver/docker-baseimage-rdesktop-web/tree/bionic-java
You can take it for a test drive with:
docker run --rm -it -p 8080:8080 lsiobase/rdesktop-web:bionic-java bash
By default it runs xterm but you can swap out the GUI app you want it to run in the autostart file , you can also install an alternative gui if need be like these containers:
As far as making something to connect to remote clients, that is not this image, just thought I would update this with the new baseimage info if others are looking