ImageAI https://academiccloud.de/de/services/imageai/) uses high-performance computing (HPC) architecture and applies the FLUX (text-to-image) and Qwen (image-to-image) models to generate images based on user instructions.

Text excerpt from the description: "Currently, the FLUX (text to image) and Qwen (image to image) models are available for the Image AI service. It has been released under Apache 2.0 and supports personal, scientific and commercial use. The user can control the behavior of the model using a system prompt. The user can also select the image dimensions (width and height) and the number of images to be generated according to their requirements."

Documentation: https://docs.hpc.gwdg.de/services/image-ai/index.html

In a nutshell: It is easy to use, generates results very quickly and is therefore well suited as an introduction to AI-based image generation (of course, the result also depends on the quality of the prompt ;-)).
And don't be confused by the note "Coming soon", the service has been in test mode for a while. 

Have fun trying it out!