the Christ/adam likeness may stem from pauls comparison and contrast, in his letters to the romans, and Corinthians.

Possibly, but medieval iconography portrays God in exactly the same way so it's more a matter of Genesis 1:27 : So God created man in his own image, in the image of God created he him; male and female created he them.

There are some lovely images in a Bodleian bestiary (Ms. Ashmole 1511, c. 1190) of the Creation in which the family resemblance is so strong it looks like Jesus having a day out at the zoo:

http://www.wga.hu/art/zgothic/miniatur/1151-200/2english/37englis.jpg