The sprites used on Alfornada battle court are menu sprites used to display the Pokemon in the player's party in Gen 1. Each menu sprite is used for multiple Pokemon, and I'll list what each Pokemon use as their menu sprite below:
Monster sprite: Charmander, Charmeleon, Charizard, Sandshrew, Sandslash, Nidoran♀, Nidorina, Nidoqueen, Nidoran♂, Nidorino, Nidoking, Zubat, Golbat, Diglett, Dugtrio, Meowth, Persian, Psyduck, Golduck, Mankey, Primeape, Poliwag, Poliwhirl, Poliwrath, Abra, Kadabra, Alakazam, Machop, Machoke, Machamp, Geodude, Graveler, Golem, Slowbro, Grimer, Muk, Gastly, Haunter, Gengar, Drowzee, Hypno, Cubone, Marowak, Hitmonlee, Hitmonchan, Lickitung, Koffing, Weezing, Rhydon, Kangaskhan, Mr. Mime, Jynx, Electabuzz, Magmar, Ditto, Porygon, Snorlax, Mewtwo, Mew
Shell sprite: Shellder, Cloyster, Staryu, Starmie, Omanyte, Omastar, Kabuto, Kabutops
Fairy sprite: Pikachu, Raichu, Clefairy, Clefable, Jigglypuff, Wigglytuff, Chansey
Bird sprite: Pidgey, Pidgeotto, Pidgeot, Spearow, Fearow, Farfetch'd, Doduo, Dodrio, Aerodactyl, Articuno, Zapdos, Moltres
Aquatic sprite: Squirtle, Wartortle, Blastoise, Tentacool, Tentacruel, Seel, Dewgong, Krabby, Kingler, Horsea, Seadra, Goldeen, Seaking, Magikarp, Lapras
Bug sprite: Caterpie, Metapod, Butterfree, Weedle, Kakuna, Beedrill, Paras, Parasect, Venonat, Venomoth, Scyther, Pinsir
Plant sprite: Bulbasaur, Ivysaur, Venusaur, Oddish, Gloom, Vileplume, Bellsprout, Weepinbell, Victreebel, Exeggcute, Exeggutor, Tangela
Serpent sprite: Ekans, Arbok, Onix, Gyarados, Dratini, Dragonair, Dragonite
Quadruped sprite: Rattata, Raticate, Vulpix, Ninetales, Growlithe, Arcanine, Ponyta, Rapidash, Slowpoke, Rhyhorn, Tauros, Eevee, Vaporeon, Jolteon, Flareon
**Ball sprite: Magnemite, Magneton, Voltorb, Electrode
Source
*In Red and Blue, Pikachu and Raichu use the Fairy sprite, whereas in yellow, they use a Pikachu menu sprite unique to them. This sprite doesn't appear on the Alfornada battle court though.
**This sprite also doesn't appear anywhere on the Alfornada battle court
