I'm currently co-writing a book that will extensively use a 32-bit art style. For ease, we've produced a sprite maker, a simple-to-use .psd file for Photoshop CS5 and above. This lets us design new character sprites quickly and easily, rather than having to make each from scratch.
Our book - Life: The Unofficial Strategy Guide - is currently on Kickstarter. If you pledge £1 then you can receive a copy of this sprite maker file when we complete our funding (April 2nd). It's essentially a pre-purchase of the sprite editor. All the donation tiers for our campaign also come with the sprite maker if you want to donate more than £1 and get your hands on a copy of the book itself.
The cover of the book (the attached image) showcases a variety of sprites, all of which were made with our sprite maker. If you're interested, take a look at the link, or share it with friends that you think might like it.