Trained Stable Diffusion on 40 pictures of various Transformers both from the movies and the old cartoon. The prompt word needed to get it to work is "TransX". Then put more detail of your choice on the Transformer you wish to see. I highly recommend you add more words to make 3d renders such as "unreal engine" or "CGI" and so on. If not the images might end up 2d instead.
Sampling steps being higher seems to produce high quality images. CFG can be anything.