Before their publication in 1993, these images were rather unknown and so-called secret paintings (18th century India) in a private collection. Stains of (menstrual?) blood on some of these paintings make them especially unique.
We have one page where you can look at these images without being hampered by words, yet should you prefer some explanation, use this page. It includes the same images but also a commentary to each one.
All these images are from The Great Book of Tantra by Indra Sinha who was able to publish these Tantric Ritual Paintings from the collection of Lance Dane.