This repo contains a few simple image generation models. You can also load any Stable Diffusion 1.5, SDXL, SD3 or Flux model into KoboldCpp.
For SD1.5 and SDXL, you only need the basic model (and VAE fix if no baked VAE). For SD3 and Flux you will also need a Clip and T5-XXL model (not included here)
You can use --sdmodel to load the base model, and check --help for other SD settings.
They are all also available in the image tab in the launcher
For a list of supported Image Generation models, please take a look at https://github.com/leejet/stable-diffusion.cpp/tree/master/docs