Following image is from a custom GPT.
Today, I received several times a message in some custom GPTs like below.
It looks custom GPTs will use 4o Image Generation soon.
Made with the old version of image generation. New images coming soon.
and
This image was created using DALL·E, OpenAI’s legacy image generation model. A newer model is rolling out soon within ChatGPT, so stay tuned for even more enhanced visuals!