The Four Living Creatures around the Heavenly Throne
The first two plates depict the throne vision of Rev 4 - 5, with the "four living creatures" surrounding God and/or the Lamb. 
The second two plates show the symbols of the four Evangelists around Jesus enthroned in Judgment (cf. Rev 19:4). 

Click on any image for a larger version.
       
      #1  
      #2  
      #3  
      #4 

Prints from Nancy Grubb's Revelations: Art of the Apocalypse (New York/London/Paris: Abbeville Publishers, 1997). 
[reproduced with permission]

#1 - Beatus of Liébana (d. 798), Commentary on the Apocalypse (Morgan Beatus), Spanish, ca. 950  [Pierpont Morgan Library, New York] 

#2 - Jacobello Alberegno (d. 1397), Vision of Saint John the Evangelist on Patmos  [Galleria dell'Accademia, Venice] - another copy here 

#3 - Jacquemart de Hesdin (d. 1409), Psalms of Penitence: Christ in Majesty, from Les Très Belles Heures du Duc de Berry, early 15th cent. French Manuscript  [Bibliothèque Royale de Belgique, Brussels] 

#4 - Christ in Majesty with Symbols of the Evangelists, from Westminster Psalter, 12th cent. English Manuscript  [The British Library, London]