At the bottom of this site there's a list of plants that are safe for bearded dragons.
Some of them aren't practical to keep in a bearded dragon enclosure, but some are! "Hens and Chicks" is a succulent, and aloe is safe too. Might be cute to get a terracotta or ceramic lil planter for a couple of succulents or an aloe vera starter?
Just make sure they don't have pesticides on them or in the soil you use to plant them in. I personally might even cover the soil in stones (big enough that lil beardie can't eat them) to make sure your dragon doesn't eat it, but I honestly don't know if that's really necessary haha
Can't wait to see pics of your lil guy and his digs!