I'll try to answer that without it turning into a long essay! So a kind of bullet point attempt.
The system is WFB, 8th ed but with various (modified) campaign lists originally part of internet forum campaigns (
'Animosity',
'Treachery and Greed' etc from around 2008 to 2014) and so not really just made up by me.
Most of the players run strong 'theme' armies, so not power gaming. We had a player who was big on that, but he ran the undead, which technically everyone else could have ganged up on, so I wanted him to. He left and so the undead are now one of the many 'NPC' forces.
Strategy, allies etc are as important if not moreso than size of armies. The NPC rulers' armies, of which there are many, are very strongly themed, and many arose from the story. For example, I had to build and paint an entire, nearly 200 model, flagellant/cultist army in robes, then later build a 50 strong mob of the same guys, who had lost a battle and been turned into zombies!
The campaign rules are very heavily modified
Mighty Empires - changed over the decades, with ideas from other systems added in, and always interpreted by the GM. Players can ask to try anything, but whether or not it is possible, and what it costs in time and money, that's for me to work out, and them to worry about!
There is one GM (me, also the story writer, photographer, army painter, model and scenery maker, etc etc) and 6 players (some close geographically who can play the rare games, some too far away and so stand ins command in tabletop encounters).
The players are effectively roleplaying one character each, who happens to be the ruler of a realm or 'other' form of force. They can die, and several have. It can then take their new character, whether or not connected to the old one, a while to establish themselves, or perhaps they just take up where the last one left off if they were in a right old pickle!
It has been nearly 6 years running. I think. Battles when we can, maybe 5 a year, due to the preparation involved, my mad detail for all the stuff in between, and the fact that we are all working, family peeps with busy RW lives!
My photo technique has developed over time, the campaign reports being a visual record. I started hiding bases about half way through and wish I had thought of it from the start!
A long and ever more complicated history recorded in battle reports and many a connecting story, plus thousands of photos like the ones you have seen, which can be viewed on the Oldhammer Forum at ...
http://forum.oldhammer.org.uk/viewtopic.php?f=15&t=2889 or on my own web site (always slightly behind but the blog part almost keeps up to date) at ...
https://www.bigsmallworlds.comPhotobucket wrecked many a forum thread with my campaign, but the people at Oldhammer rebuilt all the photos with a technical trick for which they could never understand how grateful I was and am. But I built the website of my own to try and ensure against such a disaster happening again!
Oh, and recently a member of this forum, who I have met but once in the real world in an entirely unconnected capacity, has just become a new player with a character that might become the biggest bane of all to the poor men, halflings and dwarfs of Tilea. Hopefully. The clue is, most of his forces are underground right now.