I'll have a go if you don't mind
Keep the categories where they already exist in the real world
Aviation
Naval
Land warfare
and then
Aviation
WWI
WWII
Korea
Vietnam
Gulf War
Modern
Specialist eg powerplants, uniforms, aircraft manufacturers
Biographies/autobiographies
Pictorial (photographic/illustration/fine art)
Fiction
DVDs
Naval
bit of a grey area for me but let's say you go all the way back
Naval campaigns of the ancients (eg Battle of Saramis)
British, French, Spanish and Portuguese Naval Campaigns
Naval campaigns of the US Civil War
WWI
WWII
Falklands War
Gulf War
Modern
Specialist eg (same drill)
Biographies/autobiographies
Pictorial (photographic/illustration/fine art)
Fiction
DVDs
Land warfare
Again, from all the way back to present day
Specialist eg (same drill)
Biographies/autobiographies
Pictorial (photographic/illustration/fine art)
Fiction
DVDs
Jury's still out on the Specialist section, not sure if you'd need it, get the feeling it could be covered (say, Powerplants of WWII) in the WWII section. Fiction could have its own category and so could DVDs.
As far as advertising your site, I wouldn't have a clue so dug around and found these:-
6 Ways To Advertise A Website
Could You Tell Me The Best Way To Advertise My Website
second one seems to get good reviews