Showing tips and fun facts can be good UX - distraction makes loading times seem shorter, users like learning things in a way that doesn't interrupt their tasks, and it can make the loading experience more useful, overall.
Some best practices:
- Keep the messages short enough to read in the allocated loading time, you don't them to disappear before loading is done.
- Make messages valuable, this is not the place for marketing fluff or upselling.
- If there is existing content on the screen, try not to cover it with the message.
- Be aware of tone. The user is waiting on the system, wait times cause stress. Be respectful and calming.