the pictures themselves are harmless; they're just pictures. the law also attempts to eliminate exemptions for artistic expression, rather than allow for them. simple possession of pictures or art, even if some people consider those pictures "pornographic" or "obscene", should not be criminalized in a free society. the conservative party is expressing and reflecting an irrational moral panic that the court correctly put an end to.
the crime is in trafficking and exploiting of children, not in possession. courts need to be able to correctly ascertain the difference between these behaviours, and not be restricted by moralistic sentencing laws.