Will you get a special reward for accumulating daily check ins?   [2]

If you're talking about that last scroll at the end of the month, then its the selection of 4☆ Hunters. That's the special reward. Other than that is the 3☆ selection scroll and the 10+1 scroll.

I think you mean does the rewards change from month to month, it doesn't. A 4star selection every month plus all the scrolls every week is pretty sick.