When my daughter was young I thought or maybe I wanted to save everything she did. i quickly filled one of those 'under the bed' totes that is long enough to hold wrapping paper. Periodically I've gone through that tote and was able to part with enough things that I haven't yet had to buy another tote. Not that the things in there are any less cute now than they were then, it's just that now I keep something because it was particularly wonderful or (most importantly) it had a story that I remember from it. A tote of that size or shape may not be ideal for everyone. I started out with a big one but will probably not have to buy another one to hold her artwork for years if not forever. For us this option was a good one simply because it can be stored under a bed since we do not have large closets or much space in our home for storage.
One option would be too find some hangers that you usually use to hang slacks (either the kind with the clamps or the wooden slat); paint the wooden part (if that the hanger type you chose want) a color to match your decor or leave it wooden if you choose. You can decorate the base of the hook, the clamps, or even wooden part with bows, beads, ribbon, etc. Then hang your child's artwork from the hanger. You can change the artwork as frequently as you want without ruining the picture or the walls with tape or tacks.
Another option for hanging the artwork is to hang some yarn, rope, or lightweight wire across the wall & use clothes pins to hold the artwork. You can decorate the clothes pins by gluing embellishments on them to match the room it's in or decorate clothes pins according to the season. Hang the artwork like you would hang clothes. The good thing is that whatever you are using as the "clothes line" doesn't need to be straight; actually it would look better if it weren't straight. Again you can change the artwork as frequently as you want without ruining your walls or the artwork.