You can create your own WAR as an exploded deployment (http://www.jboss.org/community/wiki/ExplodedDeployment) and place the files in there. You might have to add a mime-type to the web.xml (see the global web.xml at server/xxx/deployers/jbossweb.deployer for an example)
P.S. You never said which version of JBoss AS so I assumed the latest - 5.x. If you are using a 4.x version I'll leave you to find the global web.xml.