Based on your search query, I recommend using DreamStudio. This web-based application uses artificial intelligence to generate images from text prompts, which aligns perfectly with your need for a tool to generate images.

Here's how DreamStudio can address your needs:

• AI Image Generation: You can input a text description of the desired image, and the application will generate an image based on your input. This feature can be used to create visual representations of concepts, making them easier for students to understand.
• Adjustable Image Elements: You can adjust the style, number, and other elements of the image to create unique images for different learning materials.
• Downloadable Images: Once an image is generated, you can download it for use in your teaching materials.

As for the cost, DreamStudio operates on a credit system. New users receive 25 free credits, which should allow you to test the platform and see if it meets your needs. If you find it useful, you can purchase more credits as needed.