Hello Hans,
To install additional software when installing a server with SLES i've created some post-install scripts. Those scripts download the necessary files through HTTP and then install the software or deploy configfiles or whatever else. Works fine for me.
Another option would be to create the rpm's of your files, put them in the SLES repository and then somehow recreate an indexfile that says which files are in the repository, then you can add a <package>-line in your control file. But i haven't figured this out yet.
Rgds,
Johan
Hans