Was Walt Disney a Christian? If not, what was he?

Yes, he was a Congregationalist.

Walt Disney was born into and raised in a family of devout Congregationalists. Walt was named after the preacher at his family's Congregationalist church: Walter Parr, a close friend of his father's.

http://www.adherents.com/people/pd/Walt_Disney.html

He seems to have been what is known as a "nominal Christian," meaning he accepted his Christian heritage and did not seek another religion. There is no evidence of any great personal devotion. Evangelicals are fond of pointing out that Main Street in Disneyland has no church.

It turns out Walt Disney thought of himself as 'religious,' that is, as a Christian. Like many American Christians, however, he did not think he needed to go to church... draws on the American civil religion of 'faith in faith.'

http://dukemagazine.duke.edu/article/books-march-april-2005

Mark Pinsky, cited in the above reference, alludes to humanism as Disney's guiding light.
http://www.markpinsky.com/excerptDIS.htm

This unauthorized site claims to present his faith in his own words. The Order of DeMolay apparently influenced him as greatly as the Congregational Church.
http://www.disneydreamer.com/Waltfaith.htm