How boring this might sound, bookcovers illustrated between 1880 and 1940 are very interesting. Especially those related to fetish, bdsm and spanking.
At my facebookpage I am building on a SFW collection, here I will share the more naughty ones that are considered NSFW. Don’t forget that a lot of those published books on flagellation and spanking were banished by court during their glory days.
I hope you enjoy this very first collection, whenever there is more art (or info) to view I have attached a link to this.