Hi, Santiago,
If the documents based on the template are meant to be only one page,
or if the border and graphic should appear on every page, then anchor
them in the header (that is, have the cursor in the header paragraph
when you paste or link the graphics). Right-click the graphic and set
its text wrapping to "behind text", and then you can drag it anywhere
on the page.
If the graphic should be only on the first page, no matter how long
the document grows, then you first need to go to File > Page Setup on
the Layout tab and check the option for "Different first page". Then
anchor the graphic in the First Page Header.
In either case, the graphics will be selectable only when the header
pane is open, not during ordinary text entry.