From Inkscape .46, there is an ability to have stock patterns. This means that you can create your own patterns and make them available for use in any Inkscape drawing, not just the one the pattern was created in. Unfortunately, there is no way to construct these from the user interface, but there is a manual workaround.
The basic steps will be:
create a new drawing
make the pattern desired
convert the drawing objects to a pattern
save the drawing
open the svg drawing in a text editor
modify the pattern definition XML bounding box
copy out the pattern definition XML paste it into the patterns.svg file.
modify the definition to be recognized by Inkscape.