A very opinionated guide by icrawler.
This guide is very opinionated and you don't need to follow the exact steps I outline here.
This has been written for desktop but most of the concepts here apply to many editors as well.
For the programs, you can use pretty much any well-featured photo-editing/digital art program. Those that include:
If you want shortcuts for your GOG Galaxy games, make sure you have the "create shortcut on desktop" option checked in the Downloads tab in Galaxy's settings. If you didn't do that before installing a game, or accidentally deleted a shortcut, here's how to create one after the fact.
This is the easiest option in my opinion, especially if you already have nother GOG game's shortcut on your desktop. Just copy and paste any existing shortcut on your desktop, either by right clicking on it and choosing copy, using CTRL-C and CTRL-V, or right-click dragging to an empty space and choosing "Copy here".
(After cloning the wiki locally)
Add images to an images directory (or subdirectory below it) in your wiki repo.
In wiki page markup embed an image with this link format:
[[/images/path/to/image.ext|ALT TEXT]]