From Cariacture, Wit and Humor of a Nation in Picture, Song and Story, 1911. 

From Pick Me Up, 1895.

From Grip, 1888.

The sphinx has had enough with riddles.  From Die Bühne, 1925.   See Presumptive Conundrums: Rhetorical Math Questions + Answers.

From Ambition magazine, 1911.

Here's a well-dressed question mark from Die Bühne, 1925.

Here's a sheepish question from Agricultural Societies Newsletter, 1989.

Some other sheepish questions:

"Is this thing on?" —Bill Morris, Saltwater Cowboys, 2004

"Oh, should we?" —Managing the Generation Mix: From Collision to Collaboration, 2002

"What do you think about it all?" —Darby Hauck, The Death Cry, 1917

Joel Burget asked "Why hasn't anyone combined ellipsis / question mark to parallel the interrobang?"  Such a mark actually goes a long way back.  Here's an example from Pearson's magazine, 1909.

"Why?"  From Cassell's, 1885.

From A Survey by Max Beerbohm, 1921.

I dreamed of a mysterious letter.

From The Nation, 1960.

"That which is yet to come cannot be foretold," from Springfield High School's Resume yearbook, 1909.  See How to Hoodoo Hack a Yearbook.

I dreamed of Wodehousian inquisitive eyebrows.