If you’re talking about the art you create for the phone case:
“Your work is under copyright protection the moment it is created and fixed in a tangible form that it is perceptible either directly or with the aid of a machine or device” (copyright.gov faq).

More detail/legalese:

§ 102 . Subject matter of copyright: In general28
(a) Copyright protection subsists, in accordance with this title, in original works of authorship fixed in any tangible medium of expression, now known or later developed, from which they can be perceived, reproduced, or otherwise communicated, either directly or with the aid of a machine or device. Works of authorship include the following categories:
(1) literary works;
(2) musical works, including any accompanying words;
(3) dramatic works, including any accompanying music;
(4) pantomimes and choreographic works;
(5) pictorial, graphic, and sculptural works;
(6) motion pictures and other audiovisual works;
(7) sound recordings; and
(8) architectural works.
(b) In no case does copyright protection for an original work of authorship extend to any idea, procedure, process, system, method of operation, concept, principle, or discovery, regardless of the form in which it is described, explained, illustrated, or embodied in such work.

(copyright.gov, copyright law chapter 1)

That’s not to say that people don’t infringe on copyright all the time—and if you’re serious about keeping ownership of the work you might have to get your lawyers involved to bring actions against people violating your copyright.

If you’re wanting to trademark a logo for yourself, then I think you do need to go through some legal steps to get that, but I’m not sure on how that works.

I haven’t created anything like this, so I can’t tell you much else. Probably someone else can!

Best of luck!

@Soubresaut

Thank you so much for your advice and answer, very well appreciated! Yeah, you and me both! Ha! It will be fun, interesting, and an adventure to get this started!

If you have blueprints of your design and the idea is unique enough to qualify for a patent, that is the first thing you should apply for. Until your patent is decided upon, you are protected under “patent pending.”

After that, If you know the material you want this made out of, there are now companies specializing in 3D printing that will pop you off a prototype or two. If you find it is to your standards, they will gladly take a larger order. It’s much easier than it used to be.

We have an engineer here that knows about this stuff. If I were you, I would invite LuckyGuy to contribute to this question.

The next step is marketing, which I know nothing about.

But, like @Soubresaut above says: Beware, there be pirates out there. Aaaaaaarg!

If you can find a place to make them, you can set up an Etsy shop to start out and see how much interest there is in your designs. It might be a low-pressure way to test out styles and ways of promoting yourself. A lot of people are doing this already.

Regarding case manufacture, a google search of create phone cases turns up some businesses that will skin cases (although it also turns up retailers that will supply a single customized phone, which isn’t what you’re looking for), but I don’t know how you’d figure out which ones will offer you the best deal in terms of price and quality. That might take a bit of time to research.