This message warns you about probable issues with further script playback and monitoring.
Sometimes, after a site area has been selected, Image validation may warn about similar copies of the referenced image on a page.
As the matching mechanism relies on a coefficient of coincidence based on per-pixel comparison, there are two possible ways to resolve issues:
Re-select the image: will replace the image with another, more unique image.
Raise the sensitivity threshold: Raising the threshold of the coefficient of coincidence will sift out similar objects by decreasing degree of acceptable divergence, but may not help in cases where the differences between similar objects are quite minor.