I collected all masks, rings, chrstmas and vamentines day artefacts and reached level 10. But no more objectives appear... Do you know how to complete level 10 with more objectives ?
Edit: with the series of updates up to and including January 2015, there are now enough objectives to make it to level 11. There were a couple of objectives added in a December 2014 update:
run 5 million meters, less onerous than the 10 million one
unlock a hat
run 2000 meters without coins
and with the two in the latest update (1.12.2)
run 50,000 meters as Scarlet Fox
run 50,000 meters as Maria Selva
there were enough for me to complete level 11, which had some gem reward bonus.
Earlier answer, now no longer correct:
I don't believe there are enough tasks available to complete level 10. Previously, there weren't enough tasks to complete levels 8 and 9, but eventually with various updates, new tasks were added and thus those levels eventually became complete able. I expect it will be similar with level 10, so waiting for updates is the only solution I expect.
Level 10 is the last level. There are in all 56 objectives in the game version 1.9. So if you have completed them all, then there is nothing left. For list of objectives check on this link: http://templerun.wikia.com/wiki/Temple_Run_2