As far as I'm aware there are no open source LLMs that can generate images. There's image generation models like Stable Diffusion but those are not transformer language models so they'd be out of scope for the project

Do the underlying models support generation? If the support isn't there to begin with, the llama.cpp folks can't do anything about that.

Generating images using chat seems cumbersome when you can do it directly with something like stable diffusion