buy a cheap light, dip it in concrete, connect a colored cord and spray the inside with same color as cord...
Fill the balloon with water . This image illustrates why you don't completely fill the balloon you should always leave some room in the neck of the balloon, then as the form dries the pressure has somewhere to go and your clay wont split like that.
Candles. Use paper towel and toilet paper cores to fill with cement.
Toilettenpapierhalter aus Beton und Holz, schlichtes schönes Design, Handmade in Berlin
Cement planters by Ruffled.
Whoa! I am totally trying this! Hypertufa Design Using Stencils
Der SoLebIch-Adventskalender: "Sinnenrausch" beglückt uns mit ihrem selbst gegossen Platzteller aus Beton | SoLebIch.de
Golden moon surfaces Designs in concrete by the Berlin designer Alexis Oehler