Custom OSM Instance for Fictional Map?

Hey there, I hope this is the right forum category for my question.
I would like to create a 100% fictional Map of a city from a video game which still contains normal roads with names etc. like the real world.
I came across OSM and from how it looks, this seems to be possible. Is this possible using selfhosted OSM? If yes, what exactly would I need for that? Is there some guide?

Depends in what your final aims are.
If you want to use osm tools etc. have a look at https://wiki.openstreetmap.org/wiki/OpenGeofiction.
Otherwise use your preferred search engine and have a look at GIS tools.

There are also a lot of search results of people trying to so the same. E.g. see https://help.openstreetmap.org/questions/67727/can-i-create-a-fictional-map

Well, using OSM’s Mapping Tools and somehow hosting the tiles so my Developer can create a Leaflet Page for it

I already know about OGF, but how is this going to help me create my own map?

Well there seem to be like millions but I have no idea which one would work for my purpose

That article doesn’t really help me that much.

So all in all, I kinda want to make a custom OGF in some way?! With custom land masses and custom roads etc.
Is there some guide or something how OGF was made?

If you want a full “selfhosted OSM” then have a look at https://wiki.openstreetmap.org/wiki/The_Rails_Port . That would allow you to contribute to an OSM-like website that you control., and you could then use that data to create a map from it (using Leaflet or something else).

However, if what you want is something simpler then you don’t need to get that complicated. You could perhaps create what you wanted in JOSM, don’t upload it to OSM but draw maps locally based on it? That’s how the map legend that I created at https://map.atownsend.org.uk/maps/map/map.html#zoom=12&lat=-25.0011&lon=135.1107 started out (though some of that is now programmatically generated).

Is it possible to do this but with iD?

Not really I think, because iD can’t load and save .osm files directly. It only reads what’s needed from OSM API and tracks what has been changed in memory.

Okay. I tried making a small Map with JOSM, but there are two things:

  1. I created a map now, how can I make something I can use with Leaflet out of it now
  2. Is it possible to put an image (not multiple tiles or something, just an image) in the background?
  1. Probably with Maperitive, but first of course have a feel how it works with real OSM data.
  2. can be accomplished with PicLayer plugin (it’s a little bit awkward, but does work, toolbar buttons appear when you activate your image layer)

Okay. Both seems to be kinda working. I have one issue though. I’ve created a test map in JOSM, however in Maperitive everything appears as an Ocean. I don’t want my roads to be in the ocean. I’ve set an Administrative Boundary though. Is there anything else I need to do for my Areas to appear as Landmass?

Hi, have you set a place=island as your landmass? That’s quite essential.
Administrative boundaries don’t keep the ocean out.
https://wiki.openstreetmap.org/wiki/Tag:place%3Disland

Neither does place=island, only properly oriented natural=coastline.

An island is of course to be accompanied by a coastline, just as the wiki instructs.