WikiAves Encyclopedia of Brazilian Birds is an amazing resource of Campephilus descriptive information, photos and sounds. WikiAves represents the four species of Campephilus woodpeckers, listed below, that can be found in Brazil.
The photographs that I have seen in WikiAves are among the most spectacular ones that I've seen anywhere.
In English and Portuguese, the four species of Campephilus in WikiAves are:
Although the entry on the Cream-backed Woodpecker is rather slim (as of this posting) the others have a wealth of descriptive information. And you'll find sounds and photos for all of them. You can cut and paste the Portuguese text into your favorite web-based translator to understand the entries.