Requesting the following:
1. See that watermark in the lower right? Get rid of it. And the "Mod Love" title font? Remove that as well.
2. (OPTIONAL) I don't like having white backgrounds in wallpapers, so what I'm thinking would look nice is a psychedelic pattern of some kind in a color scheme that matches the rest of the image. I'll trust your judgement on this to find something that fits the aesthetic. If you're confident this is going to look like rubbish then don't bother and I''ll just deal with the white part.
3. IF converting it to jpg also makes the file size significantly smaller and doesn't reduce the quality of the colors then do that, too. Otherwise feel free to keep it as png.
In case it's helpful, here's the image that I started with (before running it through waifu2x twice and then resizing and cropping):
https://images.fineartamerica.com/images-medium-large-5/mod-love-atomic-kommie-comics.jpg 