I wouldn't recommend a live plant because of humidity levels and your beardie may very well tear them up, but if you really want live plants, here is the safe list:
Plants proven safe for Bearded Dragons:
Alfalfa
Astilbe
Baby's Tears
Basil (leaves and flowers)
Chinese Lantern (flowers)
Carnations (petals)
Chamomile, English
Clover
Dahlia (flowerhead)
Dandelion (leaves, flowerhead)
Day Lilies (flowers)
Dracaena (cornplant)
Fennel
Ficus (leaves)
Geranium (flowers, leaves)
Grape (leaves, fruit), (not ornamental grape ivys)
Impatiens
Johnny-Jump-Up (flowers)
Hibiscus, Tropical & Blue (flowers, leaves)
Hollyhock (leaves, flowers)
Hens and Chicks
Lavender
Maple (leaves)
Mesquite (leaves)
Mint
Mulberry (leaves)
Nasturtium (flowers, leaves)
Oregano
Pansies (flowers)
Pea, Green Bean (leaves, pods)
Peppermint
Petunia
Phlox
Pinks (petals)
Rose (petals)
Rosemary (leaves, flowers)
Sage (leaves, flowers)
Spider Plant (leaves, sap may be a skin irritant)
Split-Leaf Philodendron (leaves)
Squash / Zucchini (flowers)
Thyme (leaves, flowers)
Violets (Not African Violets (flowers, leaves)
Wandering Jew (leaves, sap may be a skin irritant)
Yucca (flowers)