There’s currently no image reviews or directory available for easy browsing.
This is because most of our images so far (especially in the figure study tool) used in the gesture drawing tools were provided by very generous photographers interested in helping to train fine artists, but some of them specified in the licensing agreement that their images were not to be displayed in any kind of archive or list. Out of respect for their artwork and their legal rights, we have complied and not added an image archive/review to the site.
As Ghostly points out, people have found a few workarounds though!