"pornographic" isn't the test, legality is...and that can get to be a complicated subject. In addition to child porn, certain other types are considered illegal in some jurisdictions (bestiality, for example). DH does allow "Adult content", but I'd be careful about assuming that all porn is safe.
Talk to your lawyer, decide what you can defend as legal, and go with that!
The McDonald's arches image may or may not be legal to post, depending upon fair use, source, etc. (plus with that one, there is a potential of trademark issues). The "music from Linkin Park" is a little clearer...without written permission from the copyright holder, posting it would be prohibited by DH TOS.
There is more info available at abuse.dreamhost.comFor most of this kind of stuff, you can either choose to err on the "safe" side, or get legal advice from one qualified to give it (most lawyers?) .
My advice is just an opinion, and is worth exactly what you have paid for it!