If you're handing over a product, or service, for a fee, then you are, by definition, selling.
I'm having trouble figuring out what you're trying to do here. It's obvious that you want to get your work out there (who doesn't?), but asking for a fee, though very small, for the use of one of your sprites and in the same motion calling yourself non-professional gives very mixed messages of what you're trying to accomplish.
There are no companies selling sprites because frankly, there's no market for it (at least not one that I've noticed). The reason several sites for 3D models exist, Turbosquid to name one, is that there actually does exist a market for it. There are people out there who either doesn't have the resources to do 3D art or don't have the know-how to do it, but still need 3D models. Be it for games, adverts or what have you.
2D Sprites are also much more tied to artstyle than 3D models. Most 2D games tend to look pretty different (excluding the occasional fan/clone game of course), so if you sell your sprite to a few devs and one or two of them makes a game that gets some notice, you will probably not sell many more of that particular sprite because people want their games to stand out.
Also, you can make drastic changes with very little when working in 3D. From something as simple as a different shader and texture combination, to something more extreme like re-sculpting an existing model. The equivalent when working in 2D would be much more time consuming and would ultimately exceed the cost of buying a spriteset in the first place.
I would instead suggest that you show some of your work and try to get some work as a freelancer if you want to make sprites and make some money at the same time. Or if all you want is to get your stuff out there and expand your portfolio, find some indie group to work with on a game. There are plenty of people out there working on stuff.
There's something I'm wondering about your sprite. It clearly isn't the actual size, since you state yourself that the actual sprite is 128x128 pixels and in png. But is it pixel art or something else (rendered 3d, vector, bitmap painting)?
Having a preview version of a work you're selling is fine. But when it comes to game assets, such as sprites, you should at least include one frame of the animation in actual size (and in png if it's pixel art), even if you slap a preview sticker on top of it. The reason is that if people are interested in your sprite, but all they see is a scaled down version less than half the size of the actual work, they're most likely going to skip over your stuff. Because they can't see what they would be paying money for.
Good luck to you.