Do you keep them in package or open them? I keep them in package and hang them on the walls. But I just realized that after I took them down to rearrange, they left stains on the wall. I'm not sure if it's dust stains or what, but I tried using Lysol wipes to clean the walls and it didn't work. Also, is there a cleaning agent one can use on the clamshell packaging without damaging it or making it cloudy?