It is instructive to go to ebay and search, under "Art" for "fine art photography". REFINE THE SEARCH for "completed listings" -- that shows what someone actually bought. Set the sort option for "highest price first". Scan thru for the ones that got bids. Zero bids means it didn't sell.
What's the overwhelming best seller?
Tits, ass, and great pecs, full frontal, size matters. God Bless America -- nothing ever changes.