THANK YOU PROF. As an artist - a professional artist who creates original work for pay, as opposed to a fanartist who does it solely for the love of it (which is a sliding scale, btw, not two separate boxes) - I will fight tooth and nail for fanartists to be treated fairly, to be granted the same rights and respect as any other artists.
Which means: commissioning artists should always always come with the assumption that the artist retains all the rights to the finished work, unless specified otherwise in the negotiations. That’s not nicety or convention, that’s the law. (at least in the US, though I know it’s not uncommon in other countries, as well)
A lot of fanartists kind of handwave this part but, in discussions like this, it’s very important to make that clear: unless specified otherwise, the buyer has no rights to display, license, print, (re)sell, or otherwise “own” the image, including the copyright or license to same. “Rights don’t belong to the artist if they’ve sold them,” sure, but commissioning an artist does not include, by default, all rights to that image. Copyright and licensing is not a single package deal like a salad bar, where you pay one low rate and get everything; rights to an image is more like an a la carte menu, unless you want to throw a bunch of money at the artist and buy the whole damn menu outright.
Many times, the negotiation is informal, like “hey can you make an [x] icon for me?” - which usually means, “can you make an image of [x] that I can use for digital display, possibly across multiple platforms?” However, the artist still retains all rights to that image (including display on their own page(s), resale, printing rights, etc), unless the buyer specifically requests exclusivity.
The only reason you can reblog someone else’s art on sharing sites like tumblr is because in signing up to the website, every user grants tumblr the right to re-display our content on other blogs/pages - it’s in the TOS that basically nobody reads. But that’s also why reposting (making a new/separate post containing) someone else’s artwork without permission is not only tacky, but it’s also illegal, because you don’t own display/distribution rights to that work.
Artists, if you’re not charging extra for exclusive rights, you are underselling your work. Licensing and copyright are important - yes, even if it’s fanart. (See: Hot Topic ripping off fanartists - that’s a violation of those fanartists’ rights, yeah? no matter who commissioned the work)
And the rest of ya’ll? stop treating artists like pretty-picture vending machines, where you pop a quarter in and hit a button and get whatever you want. You don’t own rights to shit, unless you negotiate and pay for it.
(I totally get Mid0nz being kind of bummed, though - from what I understand, it’s not that she thinks she owns the image, just that she wishes she’d gotten a signed copy, which I can grok.)