So, I asked on freenode ( #webpack ) and realised the answer before I could hear a response
│18:10:30 neildaemond | using this webpack.config.js, I end up with some files │
│ | like "27474d2c2aa69b9fff15b5748ef7be30.gif".. It all │
│ | works, but on the web server I want them to load from │
│ | another location like "domain.com/another/custom/path/2 │
│ | 7474d2c2aa69b9fff15b5748ef7be30.gif", not at root │
│ | (domain.com/27474d2c2aa69b9fff15b5748ef7be30.gif) │
│18:10:48 neildaemond | https://pastebin.com/AJKS9yf7 │
│18:23:43 neildaemond | oh, I figured it out.. an option for the file-loader. │
│ | updated the webpack.config.js to: │
│ | https://pastebin.com/GQvWF9H7 │