Once you've filled your boots with DADGAD or double drop D, why not turn your attention to an open tuning that is very popular for clawhammer acoustic guitar, open Gsus4? It is essentially the same ..
Open G tuning is an alternate tuning favored by Keith Richards and requires the guitar to be tuned to D-G-D-G-B-D. To retune into open G from standard tuning, drop the sixth, fifth and first strings ...