Since you presumably will lose some paper when you trim the print, it is probably better to set the page size to whatever is handy, and start from there.
Draw a rectangle exactly to size where you want the outline of the Jewel Case to be.
Then insert a text box where you want the Picture to be.
Save the result naming it "whatever".DOT
When you next want to make your label open a new document and choose your template.
You should be able to position where you wish to type any text and should be able to insert any picture or copy from clipboard in the text box.
Format the text box at the template stage to have no fill colour.
At some stage you may need to edit the wrap around for text.