I have several air plants in my mantises enclosures and in the past have also put them in frog, lizard and salamander terrariums. Yes, they are conpletely safe. They are not toxic and mantises do not eat plants anyway.
@MantisGirl13 They’re plants that lack roots, instead drawing moisture from the air, hence their name. They have other defining characteristics, too. They’re also called Tillandsia.
This is a pic of two air plants I had in a fire belly toad terrarium many years ago. The one blooming on the right is called Tillandensia ionantha and the one on the left is called Tillandensia caput medusae. They are bromeliads that get the majority of their moisture from the air.
I found some more pictures showing the air plants I used in the fire bellied toad tank. There were several glued to a flat piece of bark, one on the rock formation that served as a waterfall, another behind the FB toad. The last pic shows the tank from a different angle, you can just barely see the one on the waterfall rock.