Size is important too. It’s important for the bracket to properly support the shelf that it’s holding up. A common mistake is to buy brackets that are either to big or too small for the shelves. If they’re too big then they’ll stick out, and if they’re too small then the shelf could be unstable and dangerous. The projection of the bracket (the part that sticks out from the wall and holds the shelf) should extend to within an inch of the outer edge of the shelf.
You don’t have to buy decorative shelf brackets - you can make them instead. With a little imagination and some common sense, you could take many household or flea market objects and turn them into creative and unique shelf brackets. Bicycle handlebars, old baseball bats, hockey sticks and children’s toys could all be usable as brackets. Just remember that first and foremost they need to provide stable and uniform support for the shelves that they are meant to hold up.