I get what you mean. I don’t think something like that is possible out-of-box, but it’s shouldn’t be too hard to implement.
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You can add several new towns (each with unique design), in which only one set of heroes and creatures will live. There can be several designs on one map. On start you will choose one of them. In that way you will need to add many new heroes (as they will be shared among variants).
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Or you replace standard faction look by one of several mods. Then you will play only with choosen look, there will not be other looks together on map.
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Or simpliest but most hard way. You prepare several mods, which only replace town screen/dwellings graphics by having same file name. But this will require messing with dwellings coordinates on town screen and working with photoshop.
@Macron1
so i know the fors and secont options are available. I was thinking about something a little bit like the third one… Did you try doing it? I guess you are one of most experienced guys in modding here.
On forum of chineese HMM3 modding forum found this townscreen screenshot.
Looks like it’s remake of Cathedral town. But I didn’t find any other info on this. Hope it will come out. Because town screen looks good.
I re-wrote Necropolis town mod from VCMI 0.94 to 0.98f, but mod is not finished. Maybe someone wants to make missing graphics…
mediafire.com/?kawky5bdelrz9bw
I have currently 8 town mods I am playing with on my game, I am just a fan and not a programmer…but these 8 work to verying degrees of success.
Forge (classic and Modern)(I like certain aspects of each of these)
Abyss
Fairy Town
Preserve
Grove
Bastion
Asylum
I would like to see Cathedral, and something snow (Dragon Peaks perhaps…if I can figure out how to mod I will be adding some of my own such as a variation of this one, and perhaps a Jurrasic town and a Arboretum)
I am currently utilizing 9 town mods
Preserve (awesome)
Bastion (desert Egyptian town)
Fairy Town (really nice but needs its own set of heroes)
Old Forge (actually my fave of the two forges)
Modern Forge
Abyss (Ocean Mod / My fave mod so far/ seems to have fewest glitches)
Grove ( nice town)
Asylum ( another beauty)
Greenhouse (just plain fun and silly…)
with the vcmi 99 mod I have been able to make random maps with all 9 
I would be happy to add attachments to a post here if it is permissible.
Also I found a thread on heroes community for a beautiful Romanian Town I think the creator is looking to make for VCMI crosses fingers
Wait, do we have Asylum town ready? 
I have one that is working pretty darn well. It is on the town mods list. Also, in the Preserve 1.0 town, I have a suggestion for the rainbow structures special.
“The Rainbow adds +2 luck to garrison hero during a siege, and adds 350 gold per day.”
Please, describe more!
Preserve line-up is shifted to new townscreen (New Preserve), so I guess version 1.0 is abandonned (notice that doesn’t have externall dwelling at all). Some times ago I had ideas that inhabit H4 townscreen with new line-up of creatures (and give this town new name) but now I prefer create new line-up to townscreen form Another Rampart mod
And please enable private messages!
The Preserve I have is the one with the halflings that upgrade to Hobbits. I love this town!!! folder in mods says New Preserve. I believe it’s the one from the mods list here.
I honestly haven’t found any glitches in Abyss that stand out to me, I am in the process of some play testing on several mods, I will keep track of areas for improvements, and probably start a new chain.
The biggest glitch I have found so far to my frustration is the shipyard in Cove Town. It is pictured even when not built, and when it is actually in a place where you can build it, you cannot purchase a ship from it. 
Also I don’t think VCMI actually has cannons yet. (Though that doesn’t bother me too much)
Okay here is all the links to my share site I just uploaded my mods to:
mediafire.com/file/0m9etsbs5 … wn_098.zip
mediafire.com/file/4sx94nr65 … 1.0fix.zip
mediafire.com/file/bp3l99xgn … n_Town.zip
mediafire.com/file/vda3jb9nv … dForge.zip
mediafire.com/file/ls8r83u5d … WithHeroes
mediafire.com/file/faooza55p … i-0-98.zip
mediafire.com/file/58zgmal5r … e_v0.1.zip
mediafire.com/file/uewe54o22 … ve_v1.0fix
mediafire.com/file/m747i26wm … v0.99b.zip
If any of these don't work when you download, check to be sure all folders went to the right place, then let me know, in case I uploaded the wrong thing.oh cool you added heroes to the fairy town hehe. After i’d dug it up from the internet and added all of the creatures i’d totally forgotten to give it heroes!
I almost forgot. Back when i had first started learning how to add towns i had put this together.
dropbox.com/s/g97bvcvvimlzi … k.rar?dl=0
It’s the heroes 2 warlock town. Dunno if you want to use it or if it still works good since it’s been a while but help yourself.
anything new on this town? It is beautiful!!!