Here are images of known to me miscellaneous metrocards, transfers, single ride, trial cards.
Trial metrocards, both cards are made of paper and probably reflect trial colors for upcoming introduction of metrocards:
This metrocard has MTA logo on the back side and probably was trial version:
Metrocards issued for NY-NJ PATH:
Gold color front side PATH metrocards:
Private Queens Express Bus metrocard, that private company became part of MTA already.
Transfers between buses were introduced together with metrocard transfer between subway and buses as well as single ride metorcard for subway (not valid for transfer).
Before metrocards replaced tokens passengers were issued special paper transfers in event of broken train or bus or something else happened so trains were not running. Here are samples of those tickets:
Metrocard issued for New York City Council: