Wikipedia is censored (just ask the 2500 rc patrolers on any given hour). There was lengthy debate about another picture, a naked girl on bike used in the article nudism and managed to hold on despite several deletions. My own point of view is that nude pix of kids is best left for your mother to show to prospective suitors.
Album covers are designed to stand out - what next a war on Nirvana (album)?
Kid porn won't happen on Wikipedia, innocuous images may well be added and probably get removed within minutes. Even adult porn rarely finds a place on Wikipedia, see the talk page of Oral sex.
Filters probably have a place and it was someting I have discussed with editors on-wiki, say during the Depictions of Mohammed petition. Many of those pictures are illegal in some countries and could lead to a criminal conviction.
Wikipedia invariably vets itself based on the overiding principal what is good for the community.