I've used dwarf citrus before. Lovely plants, not dangerous to my knowledge. Watch the thorns! Whenever they pricked me I had an allergic reaction, and I ended up needing to get rid of mine (Meyer's lemon). They don't like being soaked all the time, and may be unhappy if the soil sits too wet (mine started failing after 3 months due to consistently moist soil). They like a drying period, and high light. Probably not a great long term candidate.
Ficus benjamina (weeping fig) is a commonly used chameleon plant. The sap may irriate your skin, so be warned! They prefer moderate to high light, and can be a touch fussy.
I've considered Japanese maple before. Pretty plants! Non toxic, though I'm not sure how well they'd do in a chameleon enclosure long term.
Red rip photinia is an evergreen shrub commonly used for outdoor hedges. Non-toxic, but I don't know how it'd do in an enclosure. Looks like it grows pretty big, pretty fast!
Olive trees (I'm assuming olea europea?) - again, safe but doubtful it'd survive long term. They're a Mediterranean plant, and actually like it a bit on the dry side.
Ferns - that's a very broad category! But I can't think of any that are actually harmful. Boston ferns are very hardy, and provide good foliage cover. Keep an eye on your cham - I've heard stories of some veileds mowing down on the fronds and swallowing huge lengths that may cause issuses
TL;DR: like
@jamest0o0 says, nothing inherently dangerous about any of those plants. But there are some very high lighting requirements for some, or enclosure incompatibilities