The quest says there's one in the schoolhouse - but there's no pink X there.

Looks like it's the final piece that is impossible to get. Just checked with my brother and he couldn't find the final one either. :(

boo :(

Oh, and in light of what I said above, it should go without saying that each person probably has 8 different locations. The game probably has something like 20 spots and chooses 8 for you each time. One could make a list to help others, but that's a bit like cheating.

The place in the museum is behind the plant, in front of the steps. Very hard to see.

the Xs are random within those spaces .. it will be a repeatable quest so you can do it over again .. but the X spots may change. Just look in all the buildings too.

Yes I got all 8 of mine within 1 minute of starting this Easter Event. As I had turned that repeatable quest in over an hour ago I can't tell you my 8 spots. But if I were you I'd look in all 4 of the Haven Squares, and inside all the buildings therein, including the upstairs of the Auction House and the Cellar of the School, and even look in at least the first square of the Zoo. The x's CAN be completely covered by stuff as was mine in the square that I already talked about and where I described it as having been at least once during this Event last year.
It is repeatable, but until you turn in in, the 20 hour countdown till the next time will not happen, so LOOK EVERYWHERE CAREFULLY.

Same here, behind the plant, couldn't see it first time I checked there..

ah thanks Justin :)