It depends on what/how you copy. Selecting a file name in a saved folder for instance and do "copy" will end as a placeholder in Inkscape after pasting. If you have an image open in a browser or viewer and copy from there it should appear as you expect it.
Beginners' Questions Pasting/copy
Inkscape.org
Why does a pasted copied item show up as a big X but not the picture??
Search shows NOTHING on copy/paste??
It depends on what/how you copy. Selecting a file name in a saved folder for instance and do "copy" will end as a placeholder in Inkscape after pasting. If you have an image open in a browser or viewer and copy from there it should appear as you expect it.