Ours are held on with strapping and few sheetrock screws since they are way overhead but they are very light weight. Picture hangers[1] would work for a small lowdown install or maybe some sort of double stick something... you would have to repaint and patch some holes/paint but its a huge difference. While we where waiting for them to be installed we just had them leaning against the walls like paintings waiting to be hanged. Even that was amazingly different.

http://www.caseyswood.com/shoppingcart/zen-cart/images/Sawto...

Offically! you do this with a thing called "Impaling Clips"

http://www.armstrong.com/pdbupimages/209751.pdf

https://acousticalsolutions.com/product/impaling-clip/

My new favorite product name