To add an image selector field to your system configuration:
<image> <label>Image</label> <show_in_default>1</show_in_default> <show_in_website>1</show_in_website> <show_in_store>0</show_in_store> <sort_order>70</sort_order> <frontend_type>image</frontend_type> <backend_model>adminhtml/system_config_backend_image</backend_model> <upload_dir config="system/filesystem/media" scope_info="1">customer/responsible_contacts</upload_dir> <base_url type="media" scope_info="1">customer/responsible_contacts</base_url> <show_in_default> <enabled>1</enabled> </show_in_default> </image>