@ dan I’m happy to make them for you.
I know that I like to accessorize, and that decals and shirts are a way to start to show some 'forge love/pride for those of us who might want to do that. I also know that it can be a lucrative side-market for a company that wants to take the time to deal with it themselves. I also know that it can be a pain to try to oversee, and allowing third parties to come up with and sell designs on their own can be seen as free advertising with zero effort.
That brings up questions of use and licensing of the Glowforge logo (trademarked? copyright? creative commons?) Will you authorize third-party use of the logo and name? Will Glowforge be issuing decals and apparel with equipment purchases (like Apple)? Selling/gifting them only to approved professionals (like RedBull)? Selling them to Everyone, as much as possible (like Monster Energy) Licensed reseller/design-house apparel (like MLB and NFL)? Limited edition runs of artist-designed shirts and stickers (like ello)?
How about other stuff, like the OP @alexbbrown 's dust-cover idea… if he designed one using the logo, would he have to/be able to get permission to sell it online? Or will y’all be selling branded accessories yourselves? Like right-height desktop roller stands for pushing long media through the pro, or heavy duty stands, carts, and travel cases?
As a commercial shop, I have to be aware of rights and licenses, and I would never sell anyone else’s design or Registered/copyright/trademark/logo/etc item without express written permission, or know that I could face legal action. Copyright law is nasty but straightforward enough here in the US. If @bohiwnmh wants to make my shirt design (and accept money for it), I’m sure he would ask for my permission and vector file, rather than just stealing the jpeg… right?