Best tattoo design software?

Hey everyone! Does anyone know if there’s a decent free program out there for designing tattoos?
I’ve actually got this tattoo image saved online, but I really want to tweak it... like, add something extra to the mix. I need a way to make that image "blend" seamlessly with another one I found...

??

Are you suggesting tattooing a "drawn" person? As in, getting someone's likeness from a photo tattooed?

Nah... So, I found this tattoo design online. What I'm thinking is, I want to toss it into some software and then basically layer some extra stuff onto the image itself...

No, having a tattoo or whatever has nothing to do with it... It’s like asking if there's a specific "app for masturbation" after downloading a porn movie. Of course there is! Windows Media Player, VLC media player, VLC media player, VLC media player... 🤷

You just need a graphic editing tool.
If the tattoo in your photo is something like this, and you need those "sharp, clean" lines, try using vector graphics software. Inkscape is free and works fine for conversions (there's even a portable version available)...
But if the tattoo is an actual image (like this, for example), then... well, you're going to need something similar to Photoshop (you'll probably need a Photoshop-type program anyway).

Once you have a decent program and if you still can't figure it out, feel free to ask...