I can save them out in whatever format, but that won't affect the look of the descreening much.
On the 4-in-1 picture 2 trees on the background become too blurry on the pictures №3 and №4. If it's not a jpg issue, maybe it's better to provide 2 alternative backgrounds for each game: 1 descreened and 1 not?
No, none of the blurring is JPG related, that's all got to do with descreening. I can add more re-sharpening to it, but it starts to add other artifacts that make it look weird.
Part of the problem is the size of these pictures. They are using the same size halftone printing as a full-size magazine picture or something, but it's just a little 2-inch picture. When you descreen an 8x10 printed image, you hardly notice the blurring (but you would if you zoom in close on something), on such a tiny image is very noticeable.
I'm thinking, since the overall object of MAME seems to be preservation anyway, we should probably just stick with nice, clean original untouched scans. If other users want to fiddle with them, they have the PNG to work from and can do what they want. And, now that I've played with it in MAME a little, the halftone doesn't really look that bad. It's only noticeable because we are playing the game one such a huge screen. If you put the real game under a giant magnifying glass, it'd look the same.
There is now a 'LoneRanger0', this is the un-altered image from the Photoshop file as I was working on it (from the 1600 dpi source). I've also added .PNGs for all 4 of them (not the 4-in-1 image though). I tried putting LoneRanger0.png in the artwork file as bg.png, but it wouldn't display correctly (just a bunch of diagonal lines), any obvious reason for that?
I'm thinking if we use PNGs originally scanned at 1600 dpi, and just left as-is, that would be the best option. At the very least, include the un-altered image in the artwork in case someone wants it.