I have been lectured by knowledgeable Scribus users
that vector files are superior to bitmaps in desktop publishing.
All the same, it appears that vector files don't work as well as
bitmaps in Scribus.
I have always had weird stuff happen with vector files
imported into scribus, and on the other hand .png files work great.
So I just quit using vector files, and always use .png's, because they work.
Now, my graphics files are mostly B & W musical examples, and I use
only .png's, and I don't have any printing problems that are visible to me.
It may well be that some other kinds of content do require vector files in
order to print properly. I tried using Lilypond for music notation, which
exports beautiful and editable .svg files, but Lilypond is simply far too hard
to use for a non-programmer. I have another (WYSIWYG) music notation
program that exports a very hi-res .png, I edit this with Gimp and am good to go.
If I have to assemble a complex graphic, I do use Inkscape quite a bit.
Inkscape also exports .png files, often I have to edit these some with
GIMP, and I keep them high resolution which is also, I think, a factor
that limits the file size of my scribus files to about 50 pages.
jack