The only limit to dressing up your dog's plain nylon collar is the ability to securely attach any embellishment. As long as an item can be permanently sewed, glued, riveted or brushed on, it's a good decoration for a collar. Use ribbon to change the color and pattern, rivets to add gemstones, studs or charms, and paint to create your own design. Use all of these items together for a seriously custom look, or keep it simple by adding only one for a toned-down look.
Clean the collar by washing it with laundry soap either in the washing machine or sink, and let it dry completely. If you are starting with a brand new collar, skip to Step 2.
Fit the collar to your dog's neck, adjusting buckles and slides as necessary to make it fit properly. It should be snug enough that it won't slip off over his head if he pulls on the leash, but loose enough that you can fit two fingers between the collar and his throat.
Measure and mark a point 1 inch away from the buckle on both sides using a piece of chalk or white pencil. Leave this inch of space next to the buckle free of any embellishments in case you need to adjust the size of the collar later, like if your dog gains weight or his fur thickens during winter.
Cut a piece of ribbon 1/2 inch longer than the distance between the two marks you made on the collar.
Hem the ribbon on each end by folding 1/4 inch of the end of the ribbon under and sewing straight across the end.
Lay the ribbon flat on the collar, making sure it is centered and the ends are evenly spaced away from the buckle.
Pin the ribbon to the collar, taking care not to move it out of position.
Sew the ribbon in place either by hand or by machine, using a needle designed for sewing denim. Alternately, use permanent fabric glue and glue the ribbon to the collar, placing a heavy book or object on top of the ribbon while it dries.
Mark the spot where you want to attach the rivet using either a white pencil or a fine-tip marker. The mark should be at the center of the rivet.
Create a small hole in the collar where the mark is using a leather hole punch, small electric drill or nail and hammer.
Push the stem or tube of the rivet through the hole from the back side of the collar.
Place the front rivet facedown on a solid surface.
Match up the stem of the rivet that you placed through the collar with the front of the rivet, pressing them lightly together.
Hammer the rivet into place by striking the bottom of the rivet where it is attached to the stem.
Lay the collar out flat on a hard surface.
Draw a pattern on the collar using a white pencil or fine-tipped marker. Alternately, tape or tack a stencil onto the collar.
Brush or squeeze fabric paint onto the collar, following the design you created or the edges of the stencil.
Wait for the paint to dry and cure completely, according to the manufacturer's directions, before placing the collar on your dog.