This is a method I have been using to remove background with Gimp a free program and have had excellent results when imported into PhotoVcarve. I hope it helps someone.
Open Gimp
Open file
Use path tool to go around image ( it looks like an old style ink pen )
Hit enter to close path
Double click on path tool icon to open tool box
Selecting edit opens node editing mode
when done editing click on edit at top in main tool bar, then select Copy visible
Now open new session in Gimp
Under edit drop down click on Paste
You should now see your image with no background
main tool bar under image drop down click autocrop
now under image use scale image and set desired size and save
now under file drop down select EXPORT AS; and export as desired format to desired location
You may now open PhotoVcarve
load image
select make background transparent
set material ( image size )
you are now ready to set your cutting parameters
Hope this helps
Glenn