For on-the-fly generation of seamless textures to use in your art projects, Iliad is a top contender. It's got a lot of controls for generating specific images, including the ability to generate seamless textures on the fly. That's really useful for iterating on character and environment concept art, so it's a good choice for a variety of visual art asset needs.
Another strong contender is Archsynth. This AI-based tool is good at generating tileable textures, and it's got a lot of other tricks up its sleeve, like AI inpainting, upsampling and text-to-image conversion. It's fast enough at rendering and has a relatively simple interface, so it's a good choice for designers trying to speed up their workflows.
If you need a full 3D solution, 3D AI Studio is worth a look. It can convert text or images into 3D assets, including textures, in a matter of seconds. Its interface is designed to be easy to use, and it's optimized for speed, so it's a good choice for game developers and animators.