Go ahead and throw carnivirous plant questions at me
I know way to much about them.
*First off, you need to be much more worried about the frog hurting your rather expensive plant, than the other way around.
Only the very largest Nepenthes (tropical piture plants) would be capeable of trapping a small or medium size frog. just watch that you dont let any large traps form where the frogs can get in. also make sure crickets dont get caught in the traps or you could lose the frog that goes in after it.
Highland Nepenthes would defiantley be the best to put in a terrarium. Most lowland species require a dip in temps at night.
Venus flytraps would not pose a threat at all, but they might not last very long of the frogs decide to sit on them. these also need a dormant period in the winter. same with sundews or butterworts. the "dew" on sundews might harm your frog if it sits in the plant, its a little bit acidic. not to mention all three of these will do much better in a bog style terrarium.
American piture plants need a dormant period in the winter, and I doubt they will do well in a terrarium. they dont look very tropical anyways.
basically....I would reccomend a small (many species will out grow a tank quickly) Highland Nepenthes, with some adult RETF. definatley no WTFs becasue they like to squish plants! and darts like to hide inside plants...not always the best idea if the plant is hungry 
Good luck, have fun, ask questions! (hope I didnt confuse anyone...)
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0.2.0. Leo
1.1.0. WTF
0.1.0. Irish Setter
2.1.0. Holland Lop Bunnies
1.1.0. House Cats
Too Many Fish!
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