Well, far be it from me to pass up any opportunity to plug the Uglies, the Indian States, but those of us fortunate enough to have been bitten by the bug have been chasing covers since the year dot. Often enough, it's in part to demonstrate that a particular stamp
was actually used, and when, but usually also for the sheer aesthetic pleasure of a nicely put together, strictly commercial cover.
Stabbing a finger at random in my scans, how about this registered cover with the first two stamps of Alwar State in India:


Or this one from Bhopal State, with the rather uncommon ¼ Anna of 1884, SG 48


with the most fascinating doodlings all over it?