I noticed that trunks are not being made? Don't know why.
So, I think that a Game of Thrones themed Trunk would be awesome! Maybe for male, you guys could do some Jon Snow "Night's Watch" clothing, and for female, maybe a Cersei's outfit?
Again, would be awesome!
Trunks were discontinued because they were not expensive enough compared to how much Subeta has to pay for the art.
There was a suggestions topic for a Cash Shop Costume section where items from a set could be bought separately like the Cash Shop Boutique items. The prices being the same as the boutique items. Nothing came of it but a number of people thought it would be nice to have something other than boutique items all the time.
The other users have already answered why costume trunks aren't being made anymore but the second post here lists both official and custom wearables based on that series: Sailor Moon / Game of Thrones inspired wearables?? [edit] Other wearables:

Tribute and reference items that exist already for A Song of Ice and Fire can be viewed here. There are actually quite a good amount of items already.
This doesn't include CWs iirc, and I'm sure there are tons of those. I don't really pay a ton of attention to those, though.