I had the same problem recently and like to share my solution because it took me a lot of time to figure it out.
1. Extract the jbpm-gwt-console-server.war
Extract the jbpm-gwt-console-server.war in <server>/standalone/deployments/ (with 7zip), make sure the directory name is jbpm-gwt-console-server.war. Remove the jbpm-gwt-console-server.war file from the directory. Start the server and test if the console iscorrectly deployed. If not re the README.txt in the deployments folder and create a jbpm-gwt-console-server.war.dodeploy file
2. Create .jars of your custom work item handlers
If you are using Eclipse you can simply right click one the file you want to have in the jar an click export. The choose "JAR file" and in the next step select all the classes you want to include. Place your *.jar files in <server>/standalone/deployments/jbpm-gwt-console-server.war/WEB-INF/lib
3. publicize your config files to the console
Put your drools.rulebase.conf, drools.session.conf, workItemHandlers.conf etc. in the <server>/standalone/deployments/jbpm-gwt-console-server.war/WEB-INFclasses/META-INF so they can be found by the console.
Please test this and watch server.log for problems (maybe I have forgotten something).
Hope this helps someone