if it's a nice flat sink, my mum always grew sedums in them. She raised them on a couple of bricks, and eventually the sedums hung over the edge - lovely.
If it's a deep modern one (e.g. not exactly a work of art), what about burying it in the soil and planting invasive but lovely plants in it e.g. mint?
Can't wait to hear if the carrot bed works! ;)