If you're looking for a platform to fill in gaps in an image, Clipdrop is a great option. The AI image editing tool has a variety of features, including generative fill that can create new imagery to fill in gaps. It also can remove backgrounds, upscale images and generate images from text prompts, making it a good option for pros and amateurs.
Another tool worth checking out is Picture it. This open-source AI art editor uses stable diffusion models to generate and edit imagery, and it's got an inpainting tool to fill in holes. It also can take guided drawing input and outpaint to extend the edges of an image, so it's good for digital artists and designers.
If you want a broader set of image editing tools, check out getimg.ai. The service has tools like AI Canvas to expand an image, Image Editor to edit details, and ControlNet to guide AI generation. It can also generate high-resolution images, and you can use community-trained AI models for different tasks.