Be that as it may... ;)
Some advice from a man in the know':
You need the ability to recieve payments quickly, and thus send out merchandise quickly. Get a paypal seller-account. I've waited up to four months for Marathon fans to get off their rear and send payment via mail for T-shirts. Once I had my paypal account, it took a matter of days for them to remember payment. I'm guessing it's because it doesn't involve walking to a bank, followed by the post office to deal with paypal. :D
Paypal also allows you to accept Credit card payments - the buyer can link a CC to their online account instead of (or in addition to) their Bank account. You never have to see/touch a Mastercard/Visa/etc number this way - only nice $$ amounts show up in your online account. These can be spent from there, or downloaded back into your hometown Bank Account via electronic funds transfer.
I'm still waiting on Sketchfactor to get back to me regading my next Marathon/Halo (this one applies to both communities) merchandise adventure.
However: I only sought the blessing of Bungie for my proposed Mara-stich on Patch because I wanted to sell to the Halo community as well.
As long as you're printing your posters for the Marathon community (and selling them, to say... Walmart) Bungie tends to leave us alone. I asked Steve Campbell (over @ Forerunners.org) a while back about this. Two T-shirt printings later, I'm still Microsoft Lawyer-free. :)
In regards to framing: I'd leave that up to the buyer on their end. Every city has a custom framing store. Even if they had to purchase a frame larger than the print, there's always cheep matting to be inlaied over the print.
Amazing stuff Anaphiel. Really, really good. I'd love to get a copy of your "Counterattack" poster at any size above 11"x17". :)
Reards,
-Blayne