The best part about it is that I'm no universal expert, I just know plants that are indigenous in the place I live in (northern Italy).
If you guys are interested you can find plenty of literature on the internet, or you can simply walk around unkept fields in spring and select plants you like the most. The ones I always suggest are those from the Ericaceae family, since they can be found pretty much worlwide, are really low maintainance and have beautiful flowers that are a beacon for bees and other pollen insects.