Reasons I like these publishers & grouped them together:
All of these publishers do not require an agent in order to submit a manuscript for a children's book. Some of these companies (like Olympia) prefer that you contract or use one of their illustrators, but they have some excellent literary works. (Some examples of their style of work can be found on beehiveillustrations.com )
Additionally, some other publishing companies such as Free Spirit have a primary, central focus on character traits & development. Free Spirit books are pretty specific and they are selective about what books they publish. I learned a lot about the book query process from doing their application process, including an extensive market analysis of any books that resembled our work, and yet differed from it.