Nero CoverDesigner can use a variety of picture formats for making new CD/DVD covers and this of course includes the common JPEG format. It is unlikely .ncd covers can be created using any other program, so using Nero CoverDesigner is your only choice in this case.
Convert JPEG bitmap image format to Nero CoverDesigner image format.
We have found one software suitable in our database for this conversion.
Microsoft Windows software - convert jpg to ncd on Windows
A design tool used to create custom labels, inlays, and booklets for CDs, DVDs
Convert from jpg file format
The table with program actions contains information about what each program is capable of doing with their files. This may be a good pointer for further searches for certain file conversions and help you find the converter you are looking for if our search result is insufficient for you. However, it is far from perfect and may sometimes show results which are not really usable because of the nature of the software handles the files. So a conversion that appears as possible, just because of matched actions, may in fact not be possible.