update (11 July 2018): According to the Namibia Professional Hunting Association (NAPHA) "the implementation of the condition on the restriction of the posting of images of trophy animals on social media made by the Minister is for now on hold, until such time that the industry has reverted back with proposed guidelines for ethical marketing practices for the hunting community." [src.]
update (03 July 2018): According to recent media reports Namibia is still planning to punish individuals who post photos with dead wild animals on social media. The country's Ministry of Environment & Tourism is working on having the Nature Conservation Ordinance 4 of 1975 amended, so that posting photos of dead wild animals on social media platforms becomes illegal.
According to the Xinhua News Agency, the official press agency of the People's Republic of China, Namibia will start to prosecute people posting trophy hunting photos on social media once the new Protection Areas and Wildlife Management Bill passes into law. The news agency quotes Namibia's Environment and Tourism Minister Pohamba Shifeta saying at a press conference on 09 August 2017 "that people who kill wildlife, whether with a permit or not, and post photos on social media and boast will face the wrath of the law [...]". We'll keep you posted!