I'm currently trying to make a pack where spells require some build/set-up and I want players to be able to discover these setups via loot in the form of maps with images of the build. I.E.

However, since maps are uniquely ID'd per world, they won't keep the images if loaded in different servers.
I wanted to ask if there is/could be a way to set up a Wand or Magic Item, which is simply a map with a certain image URL assigned to it. This way, you could use something like "/mgive egg_map" and it would give you the Image Map. Since each server will have different available map IDs, this could mean the first time you use the command it will generate this image's map ID and then use that from that point onward on the server for that 'wand'/map name? I've probably explained this quite poorly sorry, but i hope it made some sense!

I think there is!

But I'm not sure I've tried saving this as a custom item, I think it will work if you make the item yml file by hand.

The projector spell is an example of how to do this with a brush:

https://github.com/elBukkit/MagicPlugin/blob/master/Magic/src/main/resources/examples/survival/spells/projector.yml

brush: "map:64:https://magic.elmakers.com/mario.gif"

And I think that same format should work as an item- so you could /mgive that whole thing directly.

And so I think that would work as a premade item with a file like this:

mario:
  item: map:64:https://magic.elmakers.com/mario.gif

Saved in items/mario.yml .. again I don't know if I have tried this so I'm not certain, but I do think that ought to work- let me know!

Unfortunately I've not had luck :( I tried-

testimage:
  item: map:64:https://i.imgur.com/wBGn2Wp.png

As well as trying your mario one, but both only gave me an unwritten map that functions as a vanilla/crafted one