Maybe not a seal scroll.
Maybe a Summoning Scroll + 2-3 Seal frags + some coins or something. I dunno.
We already get a guaranteed one each week from chase missions. We also get fragments from Matsuri if not a whole seal scroll. Then there is Sage War. Then there is the mini-client Monday rewards that give you 5 seal frags. Then there is the Anko Test and Survival Trial which both can give out seal scrolls. Yeah, the 12th trial has given me some seal scrolls too.
Oh well, Just my opinion.
But I think the 1,000 group coins for participating in the war + 63 or whatever contributions already act like a small gift. Haha. It's just that nobody in the group shop is worth getting right now.