When it comes to picture books, just browse the library and you should come away with handfuls of great books. It seems to me that most picture books are designed for read aloud by adults, so the language is not oversimplified in the longer ones, and the reading levels are in fact relatively high. A couple of great picture book authors (other than Patricia Polacco):

Eve Bunting (although some have mature topics). I personally love the book Dandelions.

Allen Say

Tomie DePaola

David Mclimans (these are newer books--one is alphabet, one numbers. Each features endangered animals. Gorgeous artwork, brief but informative text on each page about the animal)

http://www.amazon.com/Gone-Wild-Caldecott-Honor-Book/dp/0802795633

The True Story of the Three Little Pigs

Hip Cat
http://www.amazon.com/Hip-Cat-Jonathan-London/dp/0811814890

Oh--and we love this author too: Jonathan London. In addition to the popular "Froggy" books, he also has some beautiful books that feature animals in the wild. Here's a link to one of his books:

http://www.amazon.com/Eyes-Gray-Wol...p;s=books&qid=1254029803&sr=1-14

We also love Kevin Henkes, David McPhail, Robert Munsch....

So many books...so little time [sigh]