Sylvan Dell

According to their website: The picture books that we publish are usually, but not always, fictional stories that relate to animals, nature, the environment, science, and math. All books should subtly convey an educational theme through a warm story that is fun to read and that will grab a child’s attention. 

There is also a list of what they are and are NOT looking for.

http://www.sylvandellpublishing.com/Submissions.htm