Initial IMagery tiles and Terrain for offline

We plan on changing/rendering imagery tiles in real time as the drone takes images in an offline setup. Our only concern is at the start we would like some initial imagery + dem(we are currently using .terrain files from srtm) for display. Any place from where , I could get and display imagery tiles or image would be appreciated

Could you tell me how you plan to do it? I’m creating a program to make fantasy maps with terrain, and the solution I found is to convert the pixel values ​​to an array and pass it to the terrain provider, but I’d like to see more options, and if you don’t mind, could you reply?

@Haadi_M1 , is there a reason the built-in imagery providers (bing maps aerial etc.) and the Cesium World Terrain can’t be used?

No they can be use together. If I have a folder of images and I generate a dsm from these images and then convert the dsm into .terrain files which are stored in a folder, then I can serve terrains either from CesiumWorldTerrain or DSM Terrain.