Many publishers don't allow authors to choose their illustrators nor to communicate with them.
Someone explained to me that authors and illustrators don't always see eye to eye and publishers try to ease that relationship by mediating between the two. In my view, however, this causes other problems. For example, it can be disheartening for an author to see illustrations that don't match what he or she had in mind. I imagine it's even worse to find this out once the book is printed. I have seen some picture books for children where the illustrations didn't exactly match the captions.
On the other hand, some of the illustrators I contacted had such horrible experiences working directly with authors that they refused to do so. Mostly, they said that authors are too close to their work and too demanding. I remember one illustrator giving me an unsolicited psychological evaluation from my emails. He had me figured out as a client and knew exactly what to expect if he had to work with me.
There is always a balance. Sometimes authors "see" the picture a certain way and want illustrations that match their view but, unless they can actually draw a sketch or take a photo of someone posing, they can't expect the artist to have the same mental image. I have often been pleasantly surprised at how different my artist's view of a scene can be from mine. The only time I correct him is when there is anachronism or when the illustration deviates from the actual story.
In this respect, I have found it useful to write a very detailed list of illustrations needed - stating the time of day, the place, the age of the characters, and describing the event in the most accurate way possible. In spite of this, there have been times when my explanations were insufficient and gave the artist the wrong impression about the event or the feelings of the characters to be portrayed. That's why it's good to always see and approve pencil sketches before the illustrations are finalized. My present artist is using oil paints, which is God's mercy for faulty authors like me, since some things can be changed even after the painting is completed.
Also, some authors are not too good at communication skills, while a graphic director in a publishing company is trained to do just that. Personally, I like to be totally involved. I would rather work very hard to sharpen my communication skills than relinquish this level of participation. I am very grateful for the editorial staff at Reformation Heritage Books, who has allowed me to do so from the start, even when it didn't seem like the right decision.
For my novel on Olympia Morata, which will be published by P&R this year, I was not given the choice of an illustrator and could not communicate directly with him. When P&R showed me some ideas for the cover of my book, I had to express my concerns to them, expecting them to talk to the illustrator. I was not used to this and I admit it was not easy. In this case, I have learned to yield, which I guess is a healthy thing to do.
As a bonus, my year-long search for the right illustrator for my series of children's books has left me with a group of new friends - wonderful artists who have decided not to work with me for several reasons (mostly because I cannot pay what they rightly expect and deserve), but who are gracious enough to answer my questions if I ever feel the need to contact them on any issue.
I am very grateful for Matt Abraxas, my present artist. Working with him has been a pleasure and I hope I am not too difficult a client.