What are these small things on my laundry room wall?
If those are between 1/4&quot; and 3/8&quot; in diameter, they're old plastic drywall anchors.

If your shelf covers them, don't worry at all. If they're visible, slice the flange off with a knife or chisel, push the remaining plastic into the wall cavity and spackle to fix.
If nothing else, these will tell you where your stud isn't. (And you'll really need to know that to get a secure floating shelf up.)