Big picture book publishing houses don’t accept unsolicited submissions but many of the smaller independent ones do. If you want to publish without getting an agent, see the list below.
Note – all these publishers have websites and it is a very good idea to look closely at their catalogue and read their books, as they often focus on one area of the market, e.g. board books, novelty books, colouring books, educational, series, younger children, etc… and there is often a very clear house style. Submission guidelines and word count vary a lot, so check out their guidelines or ask for them and tailor each submission accordingly.
Most of these publishers also publish young readers, middle grade, teen and non-fiction
Maverick Books (currently they are overwhelmed and have closed their doors but will probably be open to submissions again at some point)
Nosy Crow (traditional publishing and digital)
Francis Lincoln books
Oxford Uni Press
Walker Books (if you look closely at their submissions page they don’t accept unsolicited manuscripts for any other age group, but they do from picture book illustrators and writers, but don’t expect a reply unless an editor absolutely loves it! The slush pile mountain is legendary!)
Sweet Cherry Publishing (series reads only)
Newish publishers to look out for:
Fourth Wall Publishing
Flying Eye Books
Old Barn Books
Barefoot Books (not sure how open to new writers/illustrators they are but checkout their interactive studio in Oxford!)
Made in Me (digital books)
You can circumvent the ‘no unsolicited manuscripts rule’ with the big publishers by talking to them at writing conferences or any other author/publisher/agent events they might attend. Also look out for competitions, they are often sponsored/judged by an editor from a publishing house that would otherwise be closed to new writers. At the SCBWI conference, I handed a Little Tiger Press editor two stories after she facilitated a picture book writing session and she was kind enough to give me some very good feedback within two weeks! My stories would have been ignored otherwise.
If you get feedback, it is like gold dust, no matter what it says. Thank editors profusely for their time.