Christmas ornaments sometimes start looking a ltittle sad. The paint comes off in spots. If it’s a family heirloom ornament, I wouldn’t do any repairs. Honor its age along with the signs of it. Perhaps give it a special place for display away from the tree. For less precious ornaments there are lots of ways to renew them.
If it’s just a small spot you might be able to repaint it with a little fingernail polish. I keep a few bottles of cheap metallic nail polish for this. The cheap stuff works fine for this. It comes in handy for all sorts of repairs during the year too. A Christmas red polish and a white one (from French manicure kits) work well too.
If that won’t work you can spray paint the whole ornament with silver, gold, white, etc. You might need to rig up a way to hang the ornament in the cardboard spray box so that it doesn’t roll when you spray on it. You’ll need to do several light coats of paint or else it will drip & that’s not a real good look in most cases.
If none of this appeals to you, you can always decoupage whatever you like onto the ornament. Pieces of Christmas carol music looks nice. You can even decoupage tissue paper, colorful napkins, or fabric onto the ornaments. Just cut the pieces narrow enough to wrap the ornament with a minimum of wrinkles. It’s better to overlap pieces than to make folds that stick out.
There are many more ways to re-do ornaments, but most take some patience and time to do. Use your imagination & have fun with it. Or hang those less than perfect ornaments in the back of the tree!