So, here's my conundrum: the cover I've been using is art that I found on Pinterest and thought was awesome. Given that I didn't expect the story to take off like this, I didn't think it would be a problem to use it. Now it is taking off, and I find myself in a situation where I have EXTREMELY limited budget to pay for a new cover image for it.
The current cover, to avoid getting sued, is a picture of a plague doctor I found which is in the public domain.
So, possible solutions to the problem? Does anyone know if I can use an image that's not mine for this, or is that illegal? Can I use it up until the point that I receive donations (if that does, indeed, happen)? Does anyone know the legalities of this?
You can also commission a totally new cover called "cover art" as opposed to an edited cover of pre-made images, but usually this isn't offered for free and can be pricey depending on the artist. I actually do this too, but I'm just a novice and currently my free shop is closed due to other priorities. There are probably others who offer free cover art, but they're rarer than paid ones. You can check out deviantart for commissioning artists too.
As for legality, I'm no expert by any means. But yes, technically you cannot use another image according to the copyright laws in the U.S. The only time you can is what I said previously, if it explicitly says it's a commercial free or royalty free image. And especially since you are making money and are more exposed to the public as your story is becoming or is currently popular, it's a definite risk to continue using that cover.
So in short, changing it is your best course of action, so you don't have to worry that the original artist/photographer/owner doesn't find you and DMCA it or some other person who recognizes it and tells the artist.
If you're REALLY on a tight budget and have no graphic design skills, you can find public domain images and then either:
1) spend some time on some graphic design Youtube videos and figure out how colors/fonts/layout should go.
2) hire some people on Fiverr to take the images you found and photoshop them together into a cover. You might have to do multiple fiverr jobs if you want a title and stuff though.
That, or save up some good money for a bit (and use a public domain plague doctor drawing for a bit), and commission an artist. For my not-on-RRL web series, I commission an artist for the cover to every individual story, and their work is consistently fantastic. I adore it, and it fills me with pride to see art based on my creative work shine like that. That's definitely put a dent in my wallet because I've gone to some of my favorite artists, but I know well that you can find artists who will be willing to do a full illustration for as low as $70, $80 and still put out really good work. This is the path I recommend because work like that will last you a lifetime. But if you're going to be in an incredibly tight financial situation for a while, then this might not be a feasible option.