Many threads and tutorials on this site about that. (
This one for example)
But basically you will want to get a tool like WebUi, Forge, ReForge or ComfyUI, then head over to
You must be registered to see the links
or
You must be registered to see the links
and download a Base Model/ Checkpoint you like and start generating.
I'd say 99% of devs creating games with AI-generated art use that kind of On-device generation.