Did you use AI to convert the JPG to vector? Or did you do that in Inkscape? Or maybe you didn't realize you did it?
Can I ask what your goal is with this project? Because they way it was converted to vector, there are hundreds, if not thousands of very small objects (when you deconstruct it in Inkscape). If you're doing what it looks like, I mean using the JPG as a base to make a slightly different image, it would go better in Inkscape without converting it to vector. Unless there's some need for it to be all vector.....but I can't think of why.
Well, getting to the small, grainy issue -- I'm not having that experience when I open with Inkscape....which is interesting, because we're both using Windows.
When you notice that the image is really small, are you sure you're looking at it, with 100% zoom? If the canvas was zoomed out, it would look smaller, but not actually be smaller.
This can't be the issue I thought it was, because I can't find that JPG in the file. It would only happen to the imported JPG. There are some imported JPGs in the file, but they appear to be just a couple of solid white rectangles (used to make some of the clouds) (using a mask).
If you discover that you are looking at 100% zoom, and the issue is still happening, can you show us a screenshot of the problems?
Haha, you read my mind! I just saw that last attachment! That's pretty much what I'm seeing too, when I open it. It's because when it was converted to vector, and because the JPG is practically ALL gradients, it had to be broken up into chunks of solid colors. Raster gradients cannot be converted to vector gradients. Or it might be more proper to say raster gradients can't be converted to gradients in an SVG file.
Anyway, what is your ultimate goal, if you can say? It might be better to leave the JPG as a raster image, and import it whole into Inkscape. Would that work?