JOANP: yes, the children's haggadah is illustrated. The kid's favorite was the picture of the pharoah waking up to find his bed covered with frogs during the ten plagues that God sent to Egypt to pursuade pharoah to let the Israelies go. Accompanied by a song "frogs here, frogs there, frogs, frogs everywhere" sung lustily (and offkey) by everybody.
Haggadot now are routinely illustrated, the point of the Sarijevo Haggadah, as I understand it is that it was the first (known).
We don't have to know anything about seders or haggadot to read the book, except what the author tells us (it's old, beautifulul, an historic first). We "bookies are used to thinking of books in terms of what they SAY. This is quite different from looking at books as historical objects, which is different again from looking at them as works of art. Many who collect early christian manuscripts don't do so because they want to know what they say -- there are other sources for this. They do it either for their artistic or Historical value. This is the realm in which we are working.
So, their are at least three ways of looking at this book: as an object of art, as an historical artifact, and, the way that we are used to, as a conveyer of written meaning.
Even here, we will see right at the beginning of the book, there are conflicts, depending on the way the characters look at the book. If it is primarily an object of art, it should be treated one was: if primarily an historical artifact, another. But no one, as far as I've read in the book, is looking at the text to see what it says. In theory, other scholars might actuually read it, to see what, if any, changes in the content there are (like my frog song, which might show a certain historical change in the way some modern Americans view the ceremony). But that's not in the book, as far as I've read.