What is the difference between humans as "image of God" and Jesus as "image of God"? What is the difference between humans as "image of God" and Jesus as "image of God" ?

Humans are God's image:


  Genesis 1:26-27
  
  26 Then God said, “Let us make mankind in our image, in our likeness,
  so that they may rule over the fish in the sea and the birds in the
  sky, over the livestock and all the wild animals,[a] and over all the
  creatures that move along the ground.”
  
  27 So God created mankind in his own image,
      in the image of God he created them;
      male and female he created them.


Jesus is the image of God


  Colossians 1:15 Who is the image of the invisible God, the firstborn
  of every creature   2 Corinthians 4:4 in whose case the god of this
  world has blinded the minds of the unbelieving so that they might not
  see the light of the gospel of the glory of Christ, who is the image
  of God.
Answer from a specifically Catholic viewpoint:
The Catechism of the Catholic Church has many references to humans as images of God, but only a few that I have found to Jesus as the image of God:

At the time appointed by God, the only Son of the Father, the eternal Word, that is, the Word and substantial Image of the Father, became incarnate; without losing his divine nature he has assumed human nature.

(paragraph 479)

Jesus revealed that God is Father in an unheard-of sense: he is Father not only in being Creator; he is eternally Father in relation to his only Son, who is eternally Son only in relation to his Father. ...
For this reason the apostles confess Jesus to be the Word: ... as &quot;the image of the invisible God&quot;; as the &quot;radiance of the glory of God and the very stamp of his nature.&quot;

(paragraphs 240–241)
In distinction from this, humans are images of God in the sense that God has created them to be like him in certain ways:

Of all visible creatures only man is &quot;able to know and love his creator.&quot; He is &quot;the only creature on earth that God has willed for its own sake,&quot; and he alone is called to share, by knowledge and love, in God’s own life. It was for this end that he was created, and this is the fundamental reason for his dignity.

(paragraph 356)
St. Thomas Aquinas discusses the meaning of &quot;image&quot; as it pertains to the Son of God in the Summa Theologica, First Part, Question 35, Article 2, and specifically discusses the difference between &quot;image&quot; as applied to humans and &quot;image&quot; applied to the Son.
To understand the structure of Aquinas' answer, understand that the Summa is not simply a book presenting Catholic Truth monolithically and without any discussion. Aquinas presents a question (usually a question that could be answered &quot;Yes&quot; or &quot;No&quot;), and comes up with reasons why it could be answered in one particular way (typically the &quot;wrong&quot; way from his viewpoint). These possible reasons are typically called &quot;Objections&quot;. After he presents his answer, he must of course discuss why these objections are after all incorrect; and he does this in &quot;replies to the objections&quot;.
Thus, in our particular case, Aquinas asks the question: &quot;Whether the name of Image is proper to the Son?&quot;; that is, &quot;Should we be using this word to describe the Son of God in the first place?&quot; One possible objection he comes up with, which applies to your question, is this:

Objection 3: Further, man is also called the image of God, according to 1 Cor. 11:7, &quot;The man ought not to cover his head, for he is the image and the glory of God.&quot; Therefore Image is not proper to the Son.

Aquinas concludes that &quot;Image&quot; is in fact applicable to the Son,

because the Son proceeds as word, and it is essential to word to be like species with that whence it proceeds.

That is, since the Son is the Word of God, he must be the same sort of being and have the same sort of characteristics (species) as God—thus it's appropriate to call him the Image of God. In responding to the objection dealing with man as &quot;image of God&quot;, Aquinas replies,

The image of a thing may be found in something in two ways. In one way it is found in something of the same specific nature; as the image of the king is found in his son. In another way it is found in something of a different nature, as the king's image on the coin. In the first sense the Son is the Image of the Father; in the second sense man is called the image of God.

That is, humans are said to be &quot;the image of God&quot; because they are like God in certain ways (knowledge, understanding, free will, etc.); but the Son is said to be &quot;the image of God [the Father]&quot; because he is God—and has all the characteristics of God.