The keyword BREAK, parenthesis () colon : semi-colon ; and dot . go a long way. While parenthesis are used for emphasis and weight, you can also use them to bundle parts of prompts. Colon to start a list, semi-colon to terminate. Won't always work as expected, but who doesn't like to fiddle.
Use BREAK to signal a new 'layer' in your image, essentially defining a new image within the image.
E.g. using art style 'casual photo' or 'professional photo' with prompt professional portrait of a female in a colorful dress BREAK a psychedelic black and white background will yield exactly that.
Below prompt, with 'professional photo' worked for me, consistently (okay, fairly), also with more than 1 image in one run:
professional full body photo of three slender lithe females BREAK one girl is a Caucasian redhead, casual wear BREAK one girl is African in a red dress, barefoot BREAK one girl is Japanse with white hair and big boots BREAK a psychedelic black and white background
The same run, 3 images:
As you can see, you will still need to be very specific between BREAKs to prevent spilling, but I think you will get the gist...