Why don't try a custom map? There are usually have a challange for every map..
Time yourselves to see if one person can find diamonds faster then the other ( if your playing with 2 or more people ) or see how fast you can find diamond!... beat my time of less then 10 secondsgood luck since they got rid of the seed map I did this on XD
Make a obstacle course and have a boat race through it,(if 360 has boats IDK)
The sad thing is... We were playing, and we found ONE diamond! THEN, like, 15 minutes later just before we were gonna save and quit, the 360 froze on us :c
But yeah, we could see who finds a diamond first[DOUBLEPOST=1373880779,1373880752][/DOUBLEPOST]
That sounds cool!
We could try to build one ^^
Hardcore mode with no chests or painting holders allowed.