So not sure if this has been suggested before, but i just had the idea that there could be troop challenges..
-Successfully attack with 'x' troops 1,000/5,000/10,000 times.
-there also has to be a certain number, E.g 75 for any single unit, maybe 15 for giants and balloons, 20 for wizards, maybe 5 or 6 for dragons, etc, etc. (so there's a solid number of the troops being used)
-then once the challenge has be completed you can unlock both the experience, gems but also a STATUe of that troops

