Since the SDXL version was requested I thought I would do this one too.
V1 is tagged with terms like "DiscoStyle, Disco Elysyium, abstract, expressionism, painting, portrait, abstract background." Try it out with your workflow and see what works best for you. "Abstract expressionist painted portrait..." and "Harsh brushstrokes" Seems like a good starting point.
V2 is tagged with the terms "discostyle, abstract, expressionist, painterly, traditional media, harsh brushstrokes, portrait, abstract background, multicolored background."
Try "Colorful" in the positive prompt "Monochrome, muted color" in the negative prompt if you find results too dull.
I don't use base PonyXL very often, so my settings and workflow may not be best for optimal results.