Here are some links to articles about Marvin Miller cards. The only possible one to predate the 1994 Upper Deck card is the 1991 Big League Cards card shown in the first two links below. But I don't think that was a commercially issued card; Big League Cards was Jim Bouton's company that made custom cards for anybody who sent in a photo and biographical info. (See here:
http://www.jimbouton.com/cards.html) Looking up "big league cards" on eBay reveals several cards in the same style from the 80s and 90s, but none of Miller.
https://www.sbnation.com/2012/11/28/...n-miller-cards
http://crazybaseballcards.blogspot.c...d-his-own.html
http://www.jewishsportscollectibles.com/marvin-miller/