Yeah, in seam-generated projects the jndiPattern goes there, but you can use it for your own properties as well.

As the documentation says:

Sometimes we want to reuse the same components.xml file with minor changes during both deployment and testing. Seam lets you place wildcards of the form @wildcard@ in the components.xml file which can be replaced either by your Ant build script (at deployment time) or by providing a file named components.properties in the classpath (at development time). You'll see this approach used in the Seam examples.

Cheers,
-Pawel