I think that Mr and Mrs MB would be pleased to advise you with their knowledge and experience of alpines, Dorjac.

(Moongrower and Bulbaholic, for those members who don't know who I'm talking about!)

How about herbs of various kinds? I have mint in mine for obvious reasons!!

Quite a few of us have planted sinks, Aster has a fabulous pic of her sink, mine is on my pics. If you go to Goypeadia and look at container ideas you will see lots of ideas for planting. If you write 'sinks' in the search box it also directs you to members with sinks/troughs

ive got pinks(carnations) in mine and day lily's.But like Grandmange says herbs of different varieties would make it look good,
Herb ideas , Chives ,Marjoram, garlic chives, thyme, basil, coriander,parsley.
but take note that NOT all herbs are hardy.
Salad crops could also be ideal like radish , little gem lettuce, spring onions, tomatoes, cucumbers (outdoor variety), but use bamboo canes with the tomatoes and cucumbers for support.
That if you are using the deep white sink, like ive giot in pictures if you want to have a look.
My husband actually saw one of these sinks like we've got for sale in a shop for £150

Mine is in sahde so in the summer it has busy lizzies in the autumn/ winter cyclamen that I leave in the conatiner. there are crocus and pansies for spring

Thanks everyone, especially Drc and Spritz. Been out looking at Gilbert White's house at Selbourne today with stay at Godalming before visit. 20 of us to a pub dinner. Will follow up some help given here later.