Where can I find a social network image dataset? I am supervising a programming project whose goal is to detect offensive images on social networks. 
I would like to have a representative dataset of social network images. It would be best if the dataset were already classified. Otherwise, the classification of a (smallish) dataset could be a part of the project.

I looked around the internet and searched various dataset collections that are freely available, but I haven't been able to find anything appropriate.

What is the best way to get a large social network image dataset these days?
Google just released a beta search tool for datasets. This can help you find any kind of datasets you want: https://toolbox.google.com/datasetsearch