Meg, Abracabarbara is right that there are lots of variables, and not just one-way of submitting.
I used to submit traditionally (by snail mail/fed ex mostly) when I created hand built dummies. Now, I create digital dummies (create web links or PDF files) for submission and it saves me a ton of time (since I'm no longer building multiple dummies), and lots of money (no more FedEx). But I realize not all editors will accept digital dummies. If you have to snail mail it, then I would create a dummy since you have a ms and sketches.
Even if some of the spreads were left blank, the dummy itself helps them to see the pacing and page turns of your story with the text in the blank pages. If you are established with lots of art samples on your website, you'd need less art samples. If you are not established,... you'd need more art to show. (at least 3 finished art samples, and the rest could be sketches with complete text, for a submission dummy)
Short ms is not a problem! Plenty of PB's that have word counts in that range. Even wordless books are popular. You have an advantage if the work is good! A disadvantage if it is not. Has nothing to do with word count.... though PB's over 800 words are harder to sell these days, I hear.
Good luck!
ETA: One more thing. As an illustrator (who also writes), I've never submitted my ms in a text-only form... like Word. (only after a book's acquisition, and the text needs to be formatted for the editor) But in submission stage, I've only designed the text into the art/sketches so it can be read as a book).