What if terrorists used pictures of cats?

Two things to note from the lunacy of ‘social networks should tell Teresa May when someone is being a terrorist online’ and §  the ‘former global counter-terrorism director of MI6’ writing in The Guardian:

…even in the United Kingdom there are about 25 million users of Facebook and so let’s say possibly about 125m posts a day. And even if you take out all the pictures of kittens which were put up you’d still be left with an awful lot to go through

and

…people who wanted to get around restrictions placed on their communications could probably do so quite easily by using encryption.

What if they were to encrypt their communications in the pictures of cats that MI6 discard?