This is Thrilling Mystery for July 1939, no recorded artist or ISFDB entry. I found this version of the cover at Pulp Covers and checked its date in the index at Galactic Central.
This is Horror Stories for June-July 1937, cover by William F. Soare. The ISFDB entry for this issue is here. The version of the cover presented here is from this French-language collector’s site.
Update April 5, 2017. I mistakenly blogged this image before. If you go to the original post, you can see the image I meant to put up.
This is Horror Stories for November-December 1936, cover by John Howitt. The ISFDB entry for this issue is here. This version of the cover is the one preserved at Galactic Central.
My original tumblr post was here. This image was originally posted on Tumblr by Beep Boop Art and comes to us via Robotdoll’s Tumblr Toybox. Its ultimate origins remain a mystery.
My original tumblr post was here. This image is Iced by AuroBasilisk.
My original tumblr post was here. This is a sculpture Mortality is a Myth by the American artist Ted Lawson (b. 1970). Lawson maintains a professional site here. This image was first posted on tumblr by newyearoldtricks and comes to us via metalonmetalblog.
My original tumblr post was here. This image was researched by Bacchus at ErosBlog as part of the “Δ commission.” The research was originally published at Hedonix as “Δ 041 – The Space Boobies Trap.” Here is what Bacchus found.
According to this blog post where the comic is reproduced in full, this artwork is from the bottom panel of the ninth (of ten) pages of the comic Selenia by Sergio Macedo, as the comic appeared in the first issue of Heavy Metal magazine in April 1977:
Brazilian and French comic artist Sergio Macedo is profiled briefly here. See also this slightly more detailed bio and some translated quotes from interviews with the artist.
This sculpture has the look of a real-world artifact — I wish I knew where. Original post here.
Sourced to Not Pulp Covers.