Marc Michael Epstein, editor of a recent book on Jewish illuminated manuscripts, explains the symbolism used by the artists who designed these works:
The visual culture of Jews is an extension and amplification of their verbal culture. For Jews, art doesn’t merely serve to illustrate texts, . . . it actually becomes exegesis in and of itself. The illustration of the plague of frogs in the Golden Haggadah (Catalonia, ca. 1320) simultaneously illustrates 1) the biblical text, 2) the midrash that speaks of a gigantic frog that emerged from the Nile, . . . from which the other frogs emerged, and, finally, 3) [an invention added by the book’s illustrators] to polemicize against the “pharaohs” of their own time—the distinctly scatological detail of the horde of frogs emerging from the gigantic frog’s rear end.
Or—from the ridiculous to the sublime—[consider] the opening folio of the book of Numbers in the so-called Duke of Sussex Pentateuch, illuminated in the Lake Constance region around 1300, on which four knights hold banners with the symbols of the major tribes camped around each of the four sides of the Tabernacle in the wilderness. The Tabernacle is represented as a word—the opening word of the book of Numbers, vayyedabber, “and he [God] spoke.” It is thus the word of God manifest as the sacred center of everything. It literally stands in for the Tabernacle in the center of the Israelite camp, which was, after all, built to enshrine the tablets of the covenant: a physical manifestation of God’s word. It represents, by extension, the centrality of scripture—of God’s words to Moses—in the Israelite experience, in this biblical book, in the entirety of Pentateuch, and in subsequent Jewish tradition. This concept is profound in itself, but it is most fascinating that the creators of this manuscript chose to represent it visually: they chose to represent the primacy of the word in [Jewish] tradition with an image.
Read more on Book of Doctrines and Opinions: https://kavvanah.wordpress.com/2015/06/07/marc-michael-epstein-jewish-illuminated-manuscripts/