ive kept rabbits for 20 years, try curly leafed parsley, it is good for the digestive system too. general herbs are a treat too ie mint thyme(also suits chest complaints),rosemary(general tonic),chives, sage (increases milk flow).
what about flowers:
asters,dasies,geranium,hollyhock,marigolds,nasturt iums(my bunnys favorite) sunflowers.