You can give your brass charms a whole new look by antiquing them with a dark brown or black acrylic craft paint.  To do this, coat the entire piece with paint and then immediately wipe off the excess with a soft rag (old T-shirt) or paper towel leaving the paint in the crevices.  If you desire a darker look, re-antique it again.  If you got it too dark, simply scrub the paint off with a toothbrush and start over.  For a "pickled" look, try white acrylic craft paint.  Experiment with your own favorite color of acrylic craft paint. 

Charms may be painted with acrylic or metallic acrylic craft paints after antiquing.  The paint will stick better if you apply one coat of spray lacquer on the charms after antiquing them. 

You will make your charms go the distance by trying different looks on them to match the project you are working on. 

If you choose to antique or paint your charms, they must be sealed to prevent tarnishing.  You can use a spray or brush on sealer, water based varnish or polyurethane or spray lacquer.  Most of these can easily be found at a hardware store or check your local Walmart.  Your choise to select a glossy or a satin finish.  Try spraying your charms by putting them on a piece of paper in a low sided box.  Change the newspaper between each spraying.