Any advice for writing and sending pitches for comic book and graphic novel projects?
Certainly. However, I can only tell you what has worked or me with the companies through which I've published.
Rule #1 is this: Follow the guidelines to the freakin' letter. Period.
Rule #2 is this: Know your audience. Editor. Publisher. Whatever. If you do that, you can even pitch in the voice and tone of your book.
Be careful of the "Hollywood" shorthand. If your project can safely be billed as "Strawberry Shortcake meets Blade Runner" and be clear, then that's okay. If not, that shorthand gets in the way of understanding, so drop it.
Give away the ending. And don't tease. Either you put out on this date or you don't get a second call. Give it all away.
Cover the tone and theme stuff, but not at the expense of your kernal that holds the story together.
Become well trained in quickly discussing your story's plot and tone and theme in a succinct way.
For graphic novels, if requested, I also include a full issue by issue synopsis, which can be a little longer than the initial "pitch" bit. Don't get on a high horse about how that much planning and plotting ruins your creative flow. If you can't plot the story from beginning to end before you ever sit down to write it, then comics aren't the medium for you. You don't have the luxury of fudging your page count when all you get is 22 pages of roughly 4-5 panels each. You have to do the work on the front end.
List your published credits but don't sell yourself. Sell the work.
Hope this helps.