Looking for some Ideas - What should I add in my time travel mod?

I've been working on a mod called Final Epoch, which focuses on adding time travel and the overworld's natural (and soon geological) history (which is similar to earth's) in a sort of semi-vanilla style. 

Here is the Mod: https://www.curseforge.com/minecraft/mc-mods/final-epoch

Right now, I've added things like:

• Extinct Animals like Dire wolves, Trilobites and Aurochs
• Primitive Versions of villagers and pigs (which are primitive villagers and wild boars)
• 6 time periods
• a time jumper item that allows the player to travel
• And more

Feel free to drop in any thoughts and ideas related to time travel, natural history or geological history, no matter how simple, complex or even weird they may seem. Your feedback will help shape the future of this mod, thanks in advance for any support.