Take part in the British tradition of well dressing
Lantern template (Chinese lantern is good)
Pens, selotape, string (etc)
Alternatively, use real flowers!
Discuss Well Dressing (quick Google brings up loads)
Create lots of flowers and decorations from the materials you have sourced
Arrange around a local well
Alternatively, why not create the well out of cardboard for the hall and make this activity last a few weeks.