First, your typeface. Many cookbooks will feature at least two typefaces - one san serif and one cursive - on their cover.
For the text itself, Times Roman features prominently.
Second, color. If your cookbook favors a particular country's cuisine, you may want to incorporate colors from that country's flag.
Remember that full color is more expensive than black and white or spot color. Unlike today's cookbooks which feature page upon page of full color photographs, many yesteryear cookbooks restrict color to the covers. For example, the two Italian cookbooks in the third photograph above, c.1977 and c.1964 from top to bottom, have no color within their pages.
Third, illustrations. While reference cookbooks, for example, The Talisman Italian Cook Book, may not include any graphics - line drawings or photographs - most are illustrated. All promotional cookbooks, such as the two in the first photograph, have either illustrations or photographs. The softcover, The French Cookbook, has both illustrations and photographs.
Illustrations can either be black and white or color. To see more examples, check out Flickr.
Fourth, glossary and index. Most cookbooks over 50 pages have both a glossary as well as an index.
In the next Designing Your Retro Cookbook, I'll cover the recipes themselves. Good luck with designing your retro cookbook!