Shoot in landscape, not portrait.

You don't need huge photos. New phones can take photos over 8000 x 6000 pixels, which uses a lot of graphics memory. HD (1920 x 1080) is plenty. If your phone can't take smaller photos, resize them with an image editor.

Avoid things in front of the building, like trees or power lines. They make it harder to mask smoke and fire behind them.

Avoid people in the photo. People who never move break the realism of the scene.

Use JPG images.

The file extension must be .jpg, not .jpeg. If your images show up grayed out and you can't select them in Fire Studio (common on Mac), rename the extension from .jpeg to .jpg.

Keep your images in a folder inside the Fire Studio folder in Documents, for example Documents/FireStudio7/CustomBackgrounds.

Organize them however works for you: a folder per simulation, or folders by building type (residential, commercial, industrial, and so on).

Don't move images after you use them. Fire Studio remembers where each image is. If you move or rename it later, simulations that use it won't open correctly.

Don't store images on the Desktop. They're easily moved or deleted, especially on shared computers.

Don't add images straight from a USB drive. Copy them to your computer first, then add them to a custom library in Fire Studio.