This is Amazing Stories for December 1926, cover by Frank R. Paul. The ISFDB entry for this issue is here. I found this version of the cover at Pulp Covers, whose curators add the following editorial remark:

That’s right, folks. Someone painted this for no good reason, then had a contest to find some context for their insanity.

That $500 prize offered by the editors was a very rich one, assuming they were serious about it. The U.S. Department of Labor inflation calculator tells us that $500 in December 1926 would be the equivalent of $6,913.36 in May 2017.

You can read and download the entire issue from the Internet Archive.