If you're looking for an alternative to RunDiffusion, Stability AI offers a broad collection of generative AI models covering image, video, audio and language domains. Their collection includes Stable Diffusion 3, SDXL Turbo, Stable Video Diffusion, Stable Audio 2.0 and more. Stability AI offers flexible membership plans, including a free tier and a $20/month professional plan, so you can use it for whatever you need.
If you prefer an open-source approach, Picture it offers an AI art editor based on stable diffusion models. It has tools for fine-tuning image generation, guided drawing and outpainting, so it's geared for digital artists and hobbyists. The service accepts community contributions, so you can help improve it.
Finally, Dreamlike Art is a web-based AI art generator powered by Stable Diffusion. It's fast to generate images and lets you queue up lots of them for parallel processing. The service offers 50 free credits per day, but you can buy more with a subscription, so it's good for whipping up some original art.