So far I always used screenfetch for displaying system info in screenshots. The other day I found neofetch, which is very similar to screenfetch but seems to have more features and a more active development. It support Linux, MacOS, iOS, BSD, Solaris, Android, Haiku OS, GNU Hurd and Windows (Cygwin/Windows 10 Linux subsystem). Here’s how neofetch looks like on my Solus:
Neofetch is also highly customizable. See more about it and it’s customization options on it’s Github page. Most Linux distributions have it in their repositories so it should be straightforward to install.