Since there are a lot of achievements, I feel like it would give Lioden more things to do if you got items, SB or GB for earning those achievements.

There could also be achievement levels for example:

Beginner [May give something like 100SB/Common item]
- A Bun In The Oven
First successful breeding with one of your own lionesses.

Easy [May give 250SB/Uncommon item]
- A Whole New World
Take 50 explorative steps in any zone.

Moderate [May give 500SB/Rare item]
- Skill or Luck?
Win 10 NPC battles in a row.

Difficult [May give 1000SB/1GB/Extra rare item] (As you can see I couldn't think of a fitting word)
- Bountiful
Have a litter with four cubs.

Expert [May give 3,000/3GB/Special item or even lion]
- SNAAAAAAAAAKE
Complete 100 quests with the snake

Of course the prizes wouldn't have to be that they're just off the top of my head with little thought but yes I think it could be a cool little addition to the game! :)