Wonderful challenge, Beate! I chose to add a splash of yellow...the button signifies the sun added to an otherwise dreary day.
Here's what I used:
Paper: SU! Basic Gray, SU! Basic Black, Gina K. heavyweight card stock
Ink: SU! Basic Gray
Stamps: Magenta
All the other stuff: Big Shot Pro, Verve Flourished Trim A Cut Above Die, Yellow Stickles, misc. yellow button, black Hug Snug seam binding