I've been using Playground AI, and it does really well in my estimation for a free-ish service. It has paid plans that give you more image generation features, but for basic stuff, it churns out pretty good stuff and has given me a chance to make images for my rosters in large quantities. You sometimes have to spam a prompt to get fine-tuned results, but if you have to use something for large quantities (50 images per day, with the ability to do additional images after waiting 30 seconds to a minute), there might not be many more affordable solutions. Some examples: