If you're looking for a ThinkDiffusion alternative, getimg.ai is a good option. It's a full-featured image generation and editing platform with an AI Generator, Image to Video converter and an AI Canvas to expand images. It also supports more than 80 community-trained AI models and has a tiered pricing system with different credit levels.
Another option is DreamStudio. This online interface lets you create art and photos with a range of AI models, and it's got tools like inpainting, outpainting and multi-generation exploration. It also has access to the latest StableDiffusion models and a flexible canvas with heavy-duty editing abilities.
RunDiffusion is another cloud-based service that offers managed open-source AI tools, including Stable Diffusion, with an easy-to-use interface. It supports a variety of tools like Automatic1111 WebUI and Fooocus, and has tiered pricing with a free trial and subscription option. It's good for hobbyists and pros.
If you want a standalone option, DiffusionBee is a free app that runs on your machine and uses Stable Diffusion for AI art generation. It supports tools like text-to-image generation and image upsampling, and runs offline for privacy and security. That can be good if you want to keep AI generation on your own machine.