The University of Hamburg has an official logo that may only be used in compliance with certain guidelines. Notably, (according to the Bureau for Communication and Public Relations, as of February 2010) it may not be used in documents which are published under free licenses, e.g. Creative Commons.
|Release date||Jan 12th, 2012|
|Free license||Yes, CC-0|
In some document templates, there exists a special place for the logo or it might even be included by default, and its omission would result in an ugly gap. In cases where a total omission of the logo is not desirable (whatever the reason), you could instead use one of these “anti-logos”, satirical replacements for the original logo. They're visually similiar to the official logo, but are distinct enough to be immediately recognizable as satire.
I do not use these logos myself, they were created to accompany a talk about Open Access and were (not accidentally) made to appear humorous.