You need to use width and height not less than resolution 1024 but you can make it larger and that works perfectly just producing bigger battlemap.

Dimensions

You can assume battlemaps dimensions as approximately 24x24 squares (120x120 feet) for normal dimensions of specific model, for example:

1024x1024 generation is 24x24 battlemap
1536x1024 generation is 36x24 battlemap
2048x1024 generation is 48x24 battlemap

And so on.

Also sometimes square gird is visible and you can rely on this.

Prompting

Main trigger word is "Battlemap". You can try everything after this word but you can get best results generating something in medieval fantasy setting.

Two second trigger words are "Dungeon" and "Outdoor". Use the first one for closed space, usually underground (e.g. dungeons, mines, caves, castles, labyrinths, etc.) and second for open space (e.g. forest, city, sea)

Link to huggingface for 1024: https://huggingface.co/Zapper/battlemap-1024

Link to huggingface for 768: https://huggingface.co/Zapper/battlemap-768-v-10