Hi Tint,
Ok you can cut what ever you want with the program... just need create it in another program and import it.
I personally Use Illustrator for all my design work and then cut from Flexi, you can do the same just instead of flexi you would use Signgo.
I think if I recall that Signgo lite is a very cut down version of Signgo, so most of the design elements are missing. (again I may be wrong).
What do you do your main designing in? most that use a different program to the cutting program use either Illustrator or Corel Draw, but basicaly any program that can create vectors should do.
If you dont own Illustrator or Corel Draw, and dont want to shell out the money for these programs you can always try Inkscape its opensource here is the link
http://www.inkscape.org/index.php?lang=en
Just look for download button on the left hand side.
I would then check within your signgo program as to what files it can import and then ensure you save the inkscape files to that format so one can read the other and then enjoy.