There are three sizes of bases for generals in the Forward march Miniatures range. First, 15mm round commander bases that come ten to the model. Second, 20mm round bases that come ten to the model. And finally, 30mm round commander bases that come six to the model.
There are two versions for each base size. One version wear bicornes. The other version wear kepis or shakos. Before sure to give your generals some bling; a dot of gold across the top of the bicorne really sets off your officers.
Armies are organized around their officers, so you'll need to know who is in charge of what unit. Even though the models in the library are identified with files names that seem to indicate a rank or position (regimental commander, brigade commander, division commander), don't take this too seriously. Use command bases that fit into the command structure you need for your collection.
Adding the national colors to your generals' bases is a must. It adds a sense of the dramatic and makes it obvious at a quick glance who is on who's side.