You've got tons of options for plants to go along with hens and chicks....
I really like Sedums,there are tons of different varieties to choose from,my favorite is 'Cape Blanco'-It's a good filler plant.
I also like Dymondia....it's a neat ground hugging member of the daisy family,with very neat looking silvery leaves.
Another good choice is Veronica 'Georgia Blue' with it's low growth and very vivid blue flowers.
Try mixing in some larger growing Echeverias,and also Crassulas....all of these plants will grow well together.