I have also managed to get a few command bases done recently. Should need about one base per 2-3 cavalry or 3-5 infantry units. They are pretty interchangeable on the whole, although a few do have specific flags attached. Brigade bases are usually a couple of mounted figures, or perhaps a single mounted figure and one or more foot figures. Doesn't really matter as long as it looks nice. This one will serve as a CinC base as it is somewhat larger. The chap in white is actually a cavalry standard bearer with an added map, rather than his flag. The rest are brigadiers.
Apart from the Dixon's engineer officer skulking behind the gabion, all the figures are from the excellent Warfare Miniatures range.