Since the split from Codemasters I think BIS really need to work on their marketing. I could be wrong but I'm pretty sure OFP sold better than ArmA 2 and Arrowhead (OFP sold over 1 million units).
Selling merchandise sounds like an easy way to improve their brand name and products. I agree some ION stuff would be cool, as would useful things like maps, or keyboard shortcut cut-outs, mice pads, mugs, etc.
I'm not geeky enough to wear a gaming shirt in public, but others would and I think it works much better for advertising then a poster that no-one sees (especially as only people visiting some geeks rooms are thier mums lol). Ok I'm kidding as most ArmA gamers are mature average blokes. Still, mugs, pens, etc still seem like a very smart idea.
I still talk to hardcore gamers who ask me 'WTF is ArmA?'. Perhaps marketing is better in Europe or USA, but I know here in Australia is mostly non-existent, so there is a lot of room for improvement here so BIs can sell more units and get the sportscars they all deserve ;-)
BIS are you listening???