The thing about wildflowers in pasture, I would think, is considering the timing of it all.
In other words, taking into account exactly when ones' herbivores are going to be added to the paddock to mow it down. And that, of
course, depends on the types of existing pasture grasses: cool season vs warm season, as well as frequency of paddock rotation.
So what some folks might want to avoid is paying big $$$ for a mix of annuals, only to have them grazed right as they are about to flower and generate maximum pollen or nectar for the bees; since then they would neither produce bee fodder, nor go to seed, and you'd have to start from scratch every year.
That being said, for a general idea of which flowering plants are great to consider, check out the non-profit Seed Savers Exchange:
https://www.seedsavers.org/bee-feed-mix
You could then examine which flowers are in the mix, and determine which would beeee best for your pasture.
My family planted 5lbs of this seed last in various places with hopes of long term self-sowing and spreading, and the summer flowers were very brilliant. It includes both annuals and perennials.
Take note, however, that it's meant to be in a managed meadow or border setting, and not mixed into ones' pasture as the original poster desires. So clover remains most appropriate for pasture systems.