Two fundamentals determine whether your base image triggers reliably.
The first is complexity. An image dense with color variation and detail is like a fingerprint, no two are alike. That uniqueness is what the Spatial Mods viewer locks onto when scanning. The more visually rich the image, the more reliably it triggers.
The second is background. Blank or minimal backgrounds give the viewer little to recognize. If your design allows for it, avoid large areas of flat color or empty space.
Most existing print materials, packaging, posters, and brochures already meet both criteria naturally. If you are designing a base image from scratch, lead with visual richness and your trigger will take care of itself.