There are several AI tools available that can generate images for free、Some popular ones include:

1、DALLE by OpenAI: You can access it through platforms like MidJourney or DALLE mini.
2、Stable Diffusion: This is an opensource model and you can use it on platforms like AUTOMATIC1111's web UI.
3、MidJourney: It's a Discord bot that generates images based on your prompts.
4、NightCafe Creator: A webbased tool that allows you to generate images using various AI models.

Please note that while these tools are free to use, some may have limitations on the number of generations or require signing up、Always review the terms of service before using any AI tool.