As Adrian has said it is possible to find some artwork as Vectors but quite often you will have to pay for them, if it's customer supplied artwork then it might be that the original designer can provide a vector file.
Don't go purely on file format's many file formats support both bitmap & vector data so the SVG file you download may be all vectors, all bitmap or a combination of the two.
If you are looking at a centreline trace & then importing the vectors from that into vcarve you will still need some sort of software to create the centreline trace from your bitmap image, same idea as the bitmap trace in vcarve but the difference is that the resulting vectors are not the double lines. Be aware as I said before that you often don't get the results you think you are going to get.
Bitmap images are pixel based & that is generally what is used in the printing industry, Vectors are not pixel based
If you import vectors then what you do with them after you have imported them really depends on the project, that might be as simple as scaling them & then producing your toolpaths so the machine is able to cut them or importing the vectors may be just a part of your design process.