Not too much write apart from the subject description, I'm curious of how you represent your commanders on the table, particularly 17th and 18th century CnC's and wing commanders? Are you using dice frames, number of figures etc to show command structure, orders etc? Do you build a small diorama for the CnC?
In my current GNW project, I've decided that the CnC stand should have three figures on the base with a dice frame, but I'm still deciding between 1 or 2 figures on the base for the wing/brigade commanders. I don't think I'll ever need to be able to depcit three levels of command with 3, 2 and 1 figure bases, but still...
Okay its Napoleonic, but my brigade/wing commanders are single mounted figures on a penny round base, DHQs are two mounted figures on a 2p coin base. Corps commanders would be 3 or more mounted &/or foot figures, a standard bearer perhaps, on an oval base.
My 15mm Ottoman Turkish army HQ base even had a pet tiger.
For SYW I depict CinC as a 3 figure group and wing commanders as a 2 figure group with brigadiers as a single mounted officer. All on round bases - brigadier on 1p base, wing commander on larger round and CinC will be on a yet larger base.
Edward
Very much depends what the rules require.
If they wish to represent officers at brigade level and above, then usually a small cluster including the officer and a few aides de camp.
Hussars often make rather good aides de camp.
I go with the military symbol:
x = brigade, one figure
xx = division, 2 figures
xxx = corps, 3 figures
xxxx = army, 4 figures
As with others I use number of figures to represent level of command
For AWI all are on 1.5" square bases:
| Battalion | 1 figure |
| Brigade | 2 figures |
| Wing | 3 figures |
| Army | 4 figures |
For Napoleonics (6mm) all are on 1.5" square bases with a few foot figures added to give a mini-diorama:
| Brigade | 2 figures |
| Corps | 3 figures |
| Army | 4 figures |
I'd certainly go for 3 levels of command, gives you flexibility across rules. A nice little diorama base is always good for the commander - and you only need one of these per army so you can put some extra effort in.
As the others suggest increasing number of figures, and increasing base size works well. If you start with 1 figure then a 20mm base works, for 2 then 25mm sized base, and work up from there.