Even though it is a non-profit, I _think_ the donation is not considered a tax write-off because the donor is receiving something in return: a photo, a sticker, a T-shirt, advertising (blog post).
Example: Donate $100 to PBS and receive a $10 CD. Subtract the value of the CD from the donation: $90. You can claim a deduction of $90 on your taxes.
But in the case of a corporation, treating the whole thing as a marketing expense is probably easier and would yield the same result.
[I'm not a lawyer or tax accountant or any other kind of authority on taxes. Check with the IRS or competent council before filing your taxes!]
The museum aspect, non profit status etc doesn't matter. It's a legitimate marketing expense - they're paying the money to get on the front page of The Oatmeal, the same as if it went straight in The Oatmeal's pockets.