Allow 4 layers that can be configured
- Default map: Styled OSM map. Allow changing the style?
- OpenStreetMap / Wikimedia Maps
- Available local map services, use data collected in OSM
- International services
- Local providers (is there a catalog?)
- User-generated sources, such as https://openaerialmap.org/
Scanned / historical map sources T230182
Always best suggestion based on time and scale
How you can help
- Locate sources that collect aerial images from different parts of the world. GeoHack and OSM come to mind. Find out how they function, how their data could be used.