Hey, Gareth...
You should be able to just drop the files into the "graphics"
subdirectory of your custom folder, which gets automatically added to
the graphicspath setting. You can then reference the file just by
name, with no path information.
For the record, the "graphics" subdirectory can have subdirectories,
as well, all of which get added to the graphicspath, followed by the
"graphics" directory, itself. This way, you can organize your
graphics a bit without having to put extra effort into maintaining the
configuration.
-Brandon 🙂