Everything which is placed inside the deployments will not be considered by JBoss as a configurable service. However you can configure the datasource and jms destinations by deploying the "*-ds.xml" and "*-jms.xml" files. However those are not recommended ways because those are called as unmanaged services, means using console or CLI utilities oyu will not be able to manage those resources.
In order to know how to configure datasource using deployable *-ds.xml file refer to Excited about JBoss AS 7.1 Part I: Deployable Datasources
Similarly in order to know about deployable JMS resources using *-jms.xml file refer to section "Deployment of -jms.xml files" in link https://docs.jboss.org/author/display/AS71/Messaging+configuration
The deployments folder is watched for only known types of deployment packages (like .war, .ear, .jar, .rar) and it ignores the rest of the files in there. So no, that folder isn't meant for these kind of xml files.
Edit: Did not notice Jay's reply when I posted mine.