“The meaning of this word is related to the imperial seal. That seal is tantamount in authority to the actual presence of the emperor. It is not a lesser thing.”
How you arrive at this definition I'll not try to guess but according to the Biblical usage of the term it means a representation, likeness, not the thing pictured anymore than a painting is the actual person or equal to having the actual person.
It is this sense Paul uses the term “eikon” at 1 Cor. 15:49, that while fleshly, earthy they bore the “eikon”, or resembled Adam but in heaven they would bear the “eikon” or image, resemblance of the Christ.
While resembling the Christ they are lesser.
At Hebrews 1:3 Paul uses a slightly different word, “charakter” or a carved emblem, again a representation, not the thing pictured as a sculpture may show the characteristics of another but is not that person or on the same level. I Tim. 3:16 is in agreement with Paul's usage of image, “eikon”.
You may find a Greek/English lexicon and concordance useful here.