I don’t know - I think their very irregularity will be a clear hint that unlike everything else in the probe, they’re supposed to indicate something organic. The leap from there to a representation of a the sender’s form won’t be that large; at least, they’ll probably consider it a likely theory.
I think the best we could hope for is it looks to them a lot like the Voynich Manuscript.
Perhaps symmetry, paired-limbs and all, and segmentation, frequent evolutionary trends here, are not universal or common. This could change the body shapes tremendously.