A few tetras to consider are emperor tetras, black phantoms, red phantoms, rummy nose, diamonds or black skirts. Tetras, in general, should be kept in groups, no less than 5 at least with plenty of space to boot. Cories and plecos (research species first!) certainly are nice additions. Kuhli loaches, zebra loaches (Botia striata) and Botia kubotai are also a few you can consider but these don't come from the same continent as angels do so I dunno if you're really trying to go with strictly Amazon origin or intercontinental community.