Do you mean major image, the 3rd-level figment?
From the SRD:
"Because figments and glamers (see below) are unreal, they cannot produce real effects the way that other types of illusions can. They cannot cause damage to objects or creatures, support weight, provide nutrition, illuminate darkness, or provide protection from the elements. Consequently, these spells are useful for confounding or delaying foes, but useless for attacking them directly."
I would rule that the major image spell, no matter how convincing, cannot cause paralysis.