[tl;dr version of this — Copyright protects the expression, not the idea.]

If you created a 32x32 sprite and published it here on Pixeljoint, you would own the copyright to that image for however long your country of origin allows you to own a copyright. (In the United States, this means your lifetime and seventy years beyond your death.)

The Berne Convention gives you an automatic copyright to anything you create in a ‘fixed state’. (In this case, you could argue that the ‘fixed state’ equals a computer file). This gives you some leeway in pursuing a legal action against anyone who you believe infringed upon your copyrights.

Now, infringement…things get a bit tricky when we enter that area.

With larger canvasses, creating a work that has enough differences from a similar work to count as its own unique work doesn’t pose much of an issue. In a space no bigger than 16×16 or 32×32, that gets much trickier.  (You can only do so many things in such a small space.) But copyright protects the expression of an idea and not the idea itself, so if you create a 16x16 icon that looks similar to one another person created without seeing yours first (i.e. you both made essentially the same icon without knowing it), you’d both have the copyright on your specific icons.

(At this point, you’d probably want to register your work with your country’s given copyright office to have a better chance at winning any form of legal action, whether offensive or defensive.)

The issue of ‘originality’ also plays a role. Everyone creates works inspired by everyone else who came before them. Capcom fighting game sprites, the Mega Man franchise, NES games in general, and even a handful of pixel artists here on PJ and over on deviantArt have inspired my brief body of pixel work. They don’t get the copyright over my work, though. They would only get any form of credit if I explicitly lifted their work, in part or in whole, and used it in mine (at which point my work technically becomes a derivative work of their original work and we’ve stepped into copyright quicksand).

So long as you you create something unique enough to stand alone as an original design/work and don’t copy-paste someone else’s work into your own, you pretty much own the copyright on your specific piece of pixel art no matter how small the initial canvas. (Hell, you could even make an argument that a single pixel constitutes an original work if you can find a lawyer willing to defend the claim in a court of law.)

Create to your heart’s content.

[NOTE: My post here does not constitute any form of actual legal advice. I wrote my post based on years of studying copyright law as a layman. Please consult a lawyer proficient in the area of intellectual property law for actual legal advice concerning copyrights.]

Damn! Now I’ll need to study IP law and get a degree to keep myself out of any legal predicaments. So much for any free time to pixel art…