positive prompt:  HDR, 8K, high contrast, masterpiece, best quality, amazing quality, very aesthetic, vivid, surreal, abstract 
negative prompt: simple background

Consider this a background generator lora, you can use color tags like red/blue/yellow/etc background to affect the marbling color

If checkpoints ignore character tags and don't produce what you want - simply add more character specific tags, even poses, and/or lower lora strength.

Tested on Better Days checkpoint (embedded vae -> great colors, good for onsite gen), you might want to use noisy samplers, like euler a, works great with Detail Daemon (for comfyUI, for A1111/forge)

Produces grainy and noisy images, creating cool aesthetics (low res training data, okay?)

Consider using RealESRGAN_x4Plus (or 4xUltraSharp) if you really want to smooth out the noise, works fine, but the cool grainy details will be lost

about tags: liquid_marbling, high contrast, vivid are a must, if there is no/tame marbling, add surreal, abstract or crank up the detail daemon or both

Weight: 0.3~1.2

high weight (>0.5) disintegrates and warps coherent backgrounds, low weight could add nice details to those background or nothing at all, experiment