I used L-hooks (also called square bend screw hooks) set in plastic anchors in our lath and plaster walls. I had some short enough to not touch the back of the peg head between the tuning pegs but long enough to reach past the groove at the bottom of the tuner buttons.
I triple-knotted old G strings around the upper tuning pegs at the grooves and hung 'em up. If you try it, be sure to give the string a good tug to be sure it's secure! My first knots were single square knots and didn't pass the test!