I teach first grade now, but when I taught kindergarten for 7 years, this was the project that we did. I guess I never knew that a parent might think it was a silly idea.
Here's a bunch of things that my former students have done:
100 pictures of themselves - (This was incredibly cool!)
100 smiles (Same idea, a parent found 100 pictures from birth to K of their child smiling. They framed it when they were done. Precious!)
100 pennies ( I do NOT recommend this. They never stayed glue to the paper.)
100 stickers
100 baseball (or football, Pokemon, etc.) cards
100 Cheerios
100 colored toothpicks, arranged to make a picture
100 squares of colored paper, again arranged to make a picture
100 gum/candy wrappers
100 squirts of caulk (Okay, this was the strangest-sounding one, but turned out pretty cool)
100 pictures from magazines (of their favorite things, such as hunting, dolls, etc.)
100 letters cut from magazines (One girl cut out 100 M's, because her name began with M.)
100 buttons (But these also fall off pretty easily)
100 craft foam pieces
100 feathers
100 pom poms
Have fun being creative with your child!