When your aluminium foil is finished don't throw away the thick cardboard roll that is inside it. 

Cover this with adhesive felt or a gift wrap paper. Make a hole in the middle of it and put a thick straw (usually comes with sloche) in this hole. 

Buy conical and spherical styrofoam shapes for flower arrangement. 

Make a hole in the narrow end of the conical shape and fit the other end of the straw in this hole.  These long T shape arrangements can be used to display bracelet and necklace arrangements inexpensively. Picture top left.

I cut the spherical shape styrofoam in half and use the halves as seen in the top right picture.

Because styrofoam and everything else in this arrangements are quite light, to prevent these to fall down when I put the jewellery, double sided scotch tape on the bottom will help.

Either spray paint these objects or cover them with attractive paper.

You can stick velcro to the brooches and earrings or you can use long pins to attach them to the displays.