Honestly, someone should make a bot for this. It's kind of neat to do this as an interactive activity on the forum.
Like "/aiimagebot generate text" or something similar. Probably want to whitelist characters in text, because I dunno how hardened Stable Diffusion is over malicious prompts.
I haven't looked at the framework for Fediverse bots, but given that some are running around today, they must exist.
Also probably want to check with the admin on the server hosting the community, because presently, unlike comment text, those don't get cached on remote Fediverse servers, so posting a shit-ton of images to a lemmy/kbin server on an automated basis could generate long-term load.
EDIT: I take it back. The image-hosting server is the one that the poster is posting from, not the one with the community.