I can get ya all the pics you need... if you gimmee a few days. but, I don't think there's anything "behind" the windshield washer reservoir.

In front of the reservoir is a box with some fusible links in it. Is that what you mean ?

There are relays for the headlights, etc underneath a bracket behind (toward the rear of) the washer bottle, is that whatcha mean ?

See if the pics in the archive about wiring an accessory circuit will help ya any.

There are a plug or two that may not be used under there, read that post and it may tell ya what ya need to know?