I use a nail or screw (sized to hold the weight of the object being hung) to hold the picture in place, similar to what you would do at home. Then at the bottom of the picture I add velcro to hold the picture from swinging side to side up and down. My Cat has many pictures hanging in it like this since day one.
'04 Wildcat 29BHBP (Sold)
'02 Chevy 2500HD 415k miles as of Dec-18
DMax/ZF-6 Speed, CCLB, 0-70-110 HP VA Tuner, 5" exhaust, H2 Tires/Chrome Wheels (315x70-17),
B&W GN hitch and 5th Wheel Companion, BrakeSmart Brake Controller