With most models, the /v1/images/edits API only supports a single image in the image field.
However, with the new gpt-image-1 model, multiple images may be provided.
See https://platform.openai.com/docs/api-reference/images/createEdit#images-createedit-image
For gpt-image-1, each image should be a png, webp, or jpg file less than 25MB. You can provide up to 16 images.
For dall-e-2, you can only provide one image, and it should be a square png file less than 4MB.