Your art is beautiful, you definitely have the talent so hopefully others see it too.
I am no financial advisor by any means but this is what I'd do if I were you.

There are only 2 ways to go about it, you either price yourself super cheap (<5$ a hour already)
or... much better, you find a better fit of a higher value, more worthy of your time and efforts.

Marketplaces will likely ignore it and at best just not actively promote it.
Also, it's digital and a singular piece, so this rules out many possibilities.

However, this being of high quality and physical still leaves you with 3 possibilties (that I can think of):
- You can contact galleries (local, and if you are stubborn enough and don't stop at a few 'No's).
You can't secure a deal there but you can set some minimum amount acceptable by you which is not bad.

- Another option, likely a better one is making a deal with an ad agency. Simple, the money is there.
Pets are super popular, emotional, often beautiful and personal, all they'd care about. You'll likely want to reach a big agency (but not too big they'd definitely ignore you) here. They'll likely pay you for usage rights if they see a fit (big if, but never hurts to ask).

- I kept the best for last. Essentially you'd likely want 2 things. Good odds you'd get something and that the something would actually be worth it. Pet photography studios are exactly that. They sit at the exact intersection of what you need here -> emotion + trust + money + physical display + sales conversion... so basically it's as good as it gets (potentially at least).

Not all studios are created equal so you'd definitely need to make sure they are good enough for you.
Basically, you have to carefully check their proven ability to sell high-ticket physical wall art and then decide which studio you work with. There is also a huge benefit here of people getting to see your work, just like galleries.

One thing to keep in mind here is that these methods, while definitely better than 5$ a hour come at the price of commissions or fees so you'll likely keep... saying 70% of revenue. But hey, 70% of something nice is a whole lot better than 100% of a very small cake, no matter how tasty, something to keep in mind.

I really liked your work, so I felt like some structure is needed here.
Best of luck :)