Uploading custom designs

[Tiffany]

I have tried on numerous occasions to upload a design for my town flag. My town is lunasoleil so i'd like some kind of sun and moon design. But everytime I try it looks horrible. I find a pic online I like and upload it to acpatterns.com. But when I convert it to qr code its garbage. I know its not going to look the same but it doesnt even look like what it is. I'm so confused because I've seen people upload photos and all kinds of stuff and it looks great(i tried photos of my pets with the same results). Am I doing something wrong? Is there something I can do to improve the quality of the images? Is there a better site to use? Thanks