I grow many different varieties of Alstroemeria but haven't quite figured out what to plant in in zone 8B that would go extremely well with them. Any suggestions what might go well with them?

Maybe striped gazanias, catmint, lavender, blue allium, or roses.

Seems I've seen them in every kind of "mixed" floral bouquet -- with larger lilies, chrysanthemums, roses, you name it. Seems like they'd be a dainty pop of color to go with anything!

adding, if you google "flower bouquet with alstroemeria" you'll see a bunch of examples, many from 1-800 Fowers and similar commercial florists

I like Dewberry's idea of combining it with spikes of smaller blooms like lavender & catmint... or salvia, or snapdragons, or some of the showier basils...