I would totally buy an Armadyl-themed t-shirt that was subtle in its design and made out of good material that fit nicely. Of the three t-shirts I bought online, one had sleeves that flared ridiculously, one was so short that my belly would show if I had my arms anywhere that wasn't by my side or in my pockets, and one that was skin-tight.
I'd also consider an Armadyl plushie, as embarrassing as it is to admit. :]
I was wondering, if it is possible : how about bustes or statues of well known RuneScape figures?
Take a buste of General Graardor for example or a statue of Zilyana in battle pose?
It would look great to have in my glass closet with my RuneScape/RuneFest collection.
-=RuneScape and RuneFest veteran=- (20 Year Veteran cape, when?)
Whenever there is a discussion between RS3 and OSRS; remember Classic tops RS and OSRS.
Here are my personal favourites. I have for many years always checked you shop hoping for some posters or concept work but I'm glad you're finally thinking of putting them up on your store.
Real Life Skillcapes
Posters
Concept Art
Badges/Pins
Wristbands
If any of these had the option to be personally signed by a moderator or a moderator of choice (for an extra price of course) then I would imagine you could bag a few extra buyers with your merchandise.