Most setting books include a bestiary of new monsters for the heroes to fight, and while it's certainly nice to have a written description of each creature along with a little background information, this is one area where I personally like to see some artwork as well. An illustration can really help me visualize what the creatures look like, and gives me something to show to the players (or even turn into trifolds).
But it can often be difficult to find stock art that matches your monsters, and commissioning lots of custom illustrations can end up becoming prohibitively expensive.
That's why I like to cheat.
Game designers draw their inspiration from many different places, and it's not unusual to take ideas from mythology or fiction and give them your own spin. But when I created Saga of the Goblin Horde, I decided to use a slightly less orthodox source of inspiration; I browsed the stock art on DriveThruRPG.
So instead of creating a selection of monsters and then trying to find suitable artwork for them, I bought the artwork first, visualized what each creature might be like in my setting, and then wrote descriptions and stats for them.
I decided to give each monster entry a full page or half a page (depending on its importance), and each entry also has its own illustration. The only exception is the "adventurers" entry, which has two pages, as it includes stats for ten different adventurer archetypes that the goblins might encounter.
Breaking the bestiary up in this way makes it much easier to do the layout (particularly if I later realize I've forgotten a monster, and need to insert it in the right place). I also find it's much easier to navigate, as the monster names are always listed at the top of each page, so you don't need to scan through the contents of the page when looking for a specific entry.
As with the rest of the book, one of the goals of the bestiary was to provide useful information in a concise manner. I found that after adding the illustration and stat block, there was still enough space for one or two paragraphs about each creature, and that allowed me to include various rumors and revelations that the Game Master can use as adventure seeds.
I think this ties in nicely with the "low prep" style of Savage Worlds, as a GM could easily flick through the bestiary until a particular illustration catches their eye, then improvise a gaming session based on that monster, using the text as inspiration for the adventure.